xref: /dports/math/octave/octave-6.4.0/libinterp/corefcn/gl-render.cc

////////////////////////////////////////////////////////////////////////
//
// Copyright (C) 2008-2021 The Octave Project Developers
//
// See the file COPYRIGHT.md in the top-level directory of this
// distribution or <https://octave.org/copyright/>.
//
// This file is part of Octave.
//
// Octave is free software: you can redistribute it and/or modify it
// under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// Octave is distributed in the hope that it will be useful, but
// WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with Octave; see the file COPYING.  If not, see
// <https://www.gnu.org/licenses/>.
//
////////////////////////////////////////////////////////////////////////

#if defined (HAVE_CONFIG_H)
#  include "config.h"
#endif

#include <sstream>

#if defined (HAVE_WINDOWS_H)
#  define WIN32_LEAN_AND_MEAN
#  include <windows.h>
#endif

#include "lo-mappers.h"
#include "oct-locbuf.h"
#include "oct-refcount.h"

#include "errwarn.h"
#include "gl-render.h"
#include "interpreter-private.h"
#include "oct-opengl.h"
#include "text-renderer.h"

namespace octave
{
#if defined (HAVE_OPENGL)

  static int
  next_power_of_2 (int n)
  {
    int m = 1;

    while (m < n && m < std::numeric_limits<int>::max ())
      m <<= 1;

    return m;
  }

#define LIGHT_MODE GL_FRONT_AND_BACK

  // Use symbolic names for axes
  enum
  {
    X_AXIS,
    Y_AXIS,
    Z_AXIS
  };

  // Use symbolic names for color mode
  enum
  {
    UNIFORM,
    FLAT,
    INTERP,
    TEXTURE
  };

  // Use symbolic names for lighting
  enum
  {
    NONE,
    //FLAT,  // Already declared in anonymous enum for color mode
    GOURAUD = 2
  };

  // Win32 API requires the CALLBACK attributes for
  // GLU callback functions.  Define it to empty on
  // other platforms.
#if ! defined (CALLBACK)
#  define CALLBACK
#endif

  class
  opengl_texture
  {
  protected:
    class texture_rep
    {
    public:
      texture_rep (opengl_functions& glfcns)
        : m_glfcns (glfcns), id (), w (), h (), tw (), th (), tx (), ty (),
          valid (false), count (1)
      { }

      texture_rep (opengl_functions& glfcns, GLuint id_arg,
                   int w_arg, int h_arg, int tw_arg, int th_arg)
        : m_glfcns (glfcns), id (id_arg), w (w_arg), h (h_arg),
          tw (tw_arg), th (th_arg), tx (double(w)/tw), ty (double(h)/th),
          valid (true), count (1)
      { }

      ~texture_rep (void)
      {
        if (valid)
          m_glfcns.glDeleteTextures (1, &id);
      }

      void bind (int mode) const
      { if (valid) m_glfcns.glBindTexture (mode, id); }

      void tex_coord (double q, double r) const
      { if (valid) m_glfcns.glTexCoord2d (q*tx, r*ty); }

      opengl_functions& m_glfcns;
      GLuint id;
      int w, h;
      int tw, th;
      double tx, ty;
      bool valid;
      refcount<octave_idx_type> count;
    };

    texture_rep *rep;

  private:
    opengl_texture (texture_rep *_rep) : rep (_rep) { }

  public:
    opengl_texture (opengl_functions& glfcns)
      : rep (new texture_rep (glfcns)) { }

    opengl_texture (const opengl_texture& tx)
      : rep (tx.rep)
    {
      rep->count++;
    }

    ~opengl_texture (void)
    {
      if (--rep->count == 0)
        delete rep;
    }

    opengl_texture& operator = (const opengl_texture& tx)
    {
      if (&tx != this)
        {
          if (--rep->count == 0)
            delete rep;

          rep = tx.rep;
          rep->count++;
        }

      return *this;
    }

    static opengl_texture create (opengl_functions& glfcns,
                                  const octave_value& data);

    void bind (int mode = GL_TEXTURE_2D) const
    { rep->bind (mode); }

    void tex_coord (double q, double r) const
    { rep->tex_coord (q, r); }

    bool is_valid (void) const
    { return rep->valid; }
  };

  opengl_texture
  opengl_texture::create (opengl_functions& glfcns, const octave_value& data)
  {
    opengl_texture retval (glfcns);

    dim_vector dv (data.dims ());

    // Expect RGB data
    if (dv.ndims () == 3 && dv(2) == 3)
      {
        // FIXME: dim_vectors hold octave_idx_type values.
        //        Should we check for dimensions larger than intmax?
        int h, w, tw, th;
        h = dv(0), w = dv(1);

        // Return early if the image data are larger than the texture
        // can hold
        int max_size;
        glGetIntegerv (GL_MAX_TEXTURE_SIZE, &max_size);
        static bool warned = false;
        if (h > max_size || w > max_size)
          {
            if (! warned)
              {
                warning ("opengl_texture::create: the opengl library in use "
                         "doesn't support images with either dimension larger "
                         "than %d. Not rendering.", max_size);
                warned = true;
              }

            return opengl_texture (glfcns);
          }

        GLuint id;
        bool ok = true;

        tw = next_power_of_2 (w);
        th = next_power_of_2 (h);

        glfcns.glGenTextures (1, &id);
        glfcns.glBindTexture (GL_TEXTURE_2D, id);

        if (data.is_double_type ())
          {
            const NDArray xdata = data.array_value ();

            OCTAVE_LOCAL_BUFFER (GLfloat, a, (3*tw*th));

            for (int i = 0; i < h; i++)
              {
                for (int j = 0, idx = i*tw*3; j < w; j++, idx += 3)
                  {
                    a[idx]   = xdata(i,j,0);
                    a[idx+1] = xdata(i,j,1);
                    a[idx+2] = xdata(i,j,2);
                  }
              }

            glfcns.glTexImage2D (GL_TEXTURE_2D, 0, 3, tw, th, 0, GL_RGB,
                                 GL_FLOAT, a);
          }

        else if (data.is_single_type ())
          {
            const FloatNDArray xdata = data.float_array_value ();

            OCTAVE_LOCAL_BUFFER (GLfloat, a, (3*tw*th));

            for (int i = 0; i < h; i++)
              {
                for (int j = 0, idx = i*tw*3; j < w; j++, idx += 3)
                  {
                    a[idx]   = xdata(i,j,0);
                    a[idx+1] = xdata(i,j,1);
                    a[idx+2] = xdata(i,j,2);
                  }
              }

            glfcns.glTexImage2D (GL_TEXTURE_2D, 0, 3, tw, th, 0, GL_RGB,
                                 GL_FLOAT, a);
          }
        else if (data.is_uint16_type ())
          {
            const uint16NDArray xdata = data.uint16_array_value ();

            OCTAVE_LOCAL_BUFFER (GLushort, a, (3*tw*th));

            for (int i = 0; i < h; i++)
              {
                for (int j = 0, idx = i*tw*3; j < w; j++, idx += 3)
                  {
                    a[idx]   = xdata(i,j,0);
                    a[idx+1] = xdata(i,j,1);
                    a[idx+2] = xdata(i,j,2);
                  }
              }

            glfcns.glTexImage2D (GL_TEXTURE_2D, 0, 3, tw, th, 0,
                                 GL_RGB, GL_UNSIGNED_SHORT, a);
          }
        else if (data.is_uint8_type ())
          {
            const uint8NDArray xdata = data.uint8_array_value ();

            OCTAVE_LOCAL_BUFFER (GLubyte, a, (3*tw*th));

            for (int i = 0; i < h; i++)
              {
                for (int j = 0, idx = i*tw*3; j < w; j++, idx += 3)
                  {
                    a[idx]   = xdata(i,j,0);
                    a[idx+1] = xdata(i,j,1);
                    a[idx+2] = xdata(i,j,2);
                  }
              }

            glfcns.glTexImage2D (GL_TEXTURE_2D, 0, 3, tw, th, 0,
                                 GL_RGB, GL_UNSIGNED_BYTE, a);
          }
        else
          {
            ok = false;
            warning ("opengl_texture::create: invalid image data type, expected double, single, uint8, or uint16");
          }

        if (ok)
          {
            glfcns.glTexParameteri (GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
            glfcns.glTexParameteri (GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);

            if (glfcns.glGetError () != GL_NO_ERROR)
              warning ("opengl_texture::create: OpenGL error while generating texture data");
            else
              retval = opengl_texture (new texture_rep (glfcns, id, w, h, tw, th));
          }
      }
    else
      warning ("opengl_texture::create: invalid texture data size");

    return retval;
  }

  class
  opengl_tessellator
  {
  public:
#if defined (HAVE_FRAMEWORK_OPENGL) && defined (HAVE_GLUTESSCALLBACK_THREEDOTS)
    typedef GLvoid (CALLBACK *fcn) (...);
#else
    typedef void (CALLBACK *fcn) (void);
#endif

  public:

    opengl_tessellator (void) : glu_tess (nullptr), fill () { init (); }

    // No copying!

    opengl_tessellator (const opengl_tessellator&) = delete;

    opengl_tessellator operator = (const opengl_tessellator&) = delete;

    virtual ~opengl_tessellator (void)
    { if (glu_tess) gluDeleteTess (glu_tess); }

    void begin_polygon (bool filled = true)
    {
      gluTessProperty (glu_tess, GLU_TESS_BOUNDARY_ONLY,
                       (filled ? GL_FALSE : GL_TRUE));
      fill = filled;
      gluTessBeginPolygon (glu_tess, this);
    }

    void end_polygon (void) const
    { gluTessEndPolygon (glu_tess); }

    void begin_contour (void) const
    { gluTessBeginContour (glu_tess); }

    void end_contour (void) const
    { gluTessEndContour (glu_tess); }

    void add_vertex (double *loc, void *data) const
    { gluTessVertex (glu_tess, loc, data); }

  protected:
    virtual void begin (GLenum /*type*/) { }

    virtual void end (void) { }

    virtual void vertex (void * /*data*/) { }

    virtual void combine (GLdouble [3] /*c*/, void * [4] /*data*/,
                          GLfloat  [4] /*w*/, void ** /*out_data*/) { }

    virtual void edge_flag (GLboolean /*flag*/) { }

    virtual void error (GLenum err)
    { ::error ("OpenGL tessellation error (%d)", err); }

    virtual void init (void)
    {
      glu_tess = gluNewTess ();

      gluTessCallback (glu_tess, GLU_TESS_BEGIN_DATA,
                       reinterpret_cast<fcn> (tess_begin));
      gluTessCallback (glu_tess, GLU_TESS_END_DATA,
                       reinterpret_cast<fcn> (tess_end));
      gluTessCallback (glu_tess, GLU_TESS_VERTEX_DATA,
                       reinterpret_cast<fcn> (tess_vertex));
      gluTessCallback (glu_tess, GLU_TESS_COMBINE_DATA,
                       reinterpret_cast<fcn> (tess_combine));
      gluTessCallback (glu_tess, GLU_TESS_EDGE_FLAG_DATA,
                       reinterpret_cast<fcn> (tess_edge_flag));
      gluTessCallback (glu_tess, GLU_TESS_ERROR_DATA,
                       reinterpret_cast<fcn> (tess_error));
    }

    bool is_filled (void) const { return fill; }

  private:
    static void CALLBACK tess_begin (GLenum type, void *t)
    { reinterpret_cast<opengl_tessellator *> (t)->begin (type); }

    static void CALLBACK tess_end (void *t)
    { reinterpret_cast<opengl_tessellator *> (t)->end (); }

    static void CALLBACK tess_vertex (void *v, void *t)
    { reinterpret_cast<opengl_tessellator *> (t)->vertex (v); }

    static void CALLBACK tess_combine (GLdouble c[3], void *v[4], GLfloat w[4],
                                       void **out,  void *t)
    { reinterpret_cast<opengl_tessellator *> (t)->combine (c, v, w, out); }

    static void CALLBACK tess_edge_flag (GLboolean flag, void *t)
    { reinterpret_cast<opengl_tessellator *> (t)->edge_flag (flag); }

    static void CALLBACK tess_error (GLenum err, void *t)
    { reinterpret_cast<opengl_tessellator *> (t)->error (err); }

  private:

    GLUtesselator *glu_tess;
    bool fill;
  };

  class
  vertex_data
  {
  public:
    class vertex_data_rep
    {
    public:
      Matrix coords;
      Matrix color;
      Matrix vertex_normal;
      Matrix face_normal;
      double alpha;
      float ambient;
      float diffuse;
      float specular;
      float specular_exp;
      float specular_color_refl;

      // reference counter
      refcount<octave_idx_type> count;

      vertex_data_rep (void)
        : coords (), color (), vertex_normal (), face_normal (), alpha (),
          ambient (), diffuse (), specular (), specular_exp (),
          specular_color_refl (), count (1) { }

      vertex_data_rep (const Matrix& c, const Matrix& col, const Matrix& vn,
                       const Matrix& fn, double a, float as, float ds, float ss,
                       float se, float scr)
        : coords (c), color (col), vertex_normal (vn), face_normal (fn),
          alpha (a), ambient (as), diffuse (ds), specular (ss),
          specular_exp (se), specular_color_refl (scr), count (1) { }
    };

  private:
    vertex_data_rep *rep;

    vertex_data_rep * nil_rep (void) const
    {
      static vertex_data_rep *nr = new vertex_data_rep ();

      return nr;
    }

  public:
    vertex_data (void) : rep (nil_rep ())
    { rep->count++; }

    vertex_data (const vertex_data& v) : rep (v.rep)
    { rep->count++; }

    vertex_data (const Matrix& c, const Matrix& col, const Matrix& vn,
                 const Matrix& fn, double a, float as, float ds, float ss,
                 float se, float scr)
      : rep (new vertex_data_rep (c, col, vn, fn, a, as, ds, ss, se, scr))
    { }

    vertex_data (vertex_data_rep *new_rep)
      : rep (new_rep) { }

    ~vertex_data (void)
    {
      if (--rep->count == 0)
        delete rep;
    }

    vertex_data& operator = (const vertex_data& v)
    {
      if (&v != this)
        {
          if (--rep->count == 0)
            delete rep;

          rep = v.rep;
          rep->count++;
        }

      return *this;
    }

    vertex_data_rep * get_rep (void) const { return rep; }
  };

  class
  opengl_renderer::patch_tessellator : public opengl_tessellator
  {
  public:
    patch_tessellator (opengl_renderer *r, int cmode, int lmode, bool fl,
                       float idx = 0.0)
      : opengl_tessellator (), renderer (r),
        color_mode (cmode), light_mode (lmode), face_lighting (fl), index (idx),
        first (true), tmp_vdata ()
    { }

  protected:
    void begin (GLenum type)
    {
      opengl_functions& glfcns = renderer->get_opengl_functions ();

      //printf ("patch_tessellator::begin (%d)\n", type);
      first = true;

      if (color_mode == INTERP || light_mode == GOURAUD)
        glfcns.glShadeModel (GL_SMOOTH);
      else
        glfcns.glShadeModel (GL_FLAT);

      if (is_filled ())
        renderer->set_polygon_offset (true, index);

      glfcns.glBegin (type);
    }

    void end (void)
    {
      opengl_functions& glfcns = renderer->get_opengl_functions ();

      //printf ("patch_tessellator::end\n");
      glfcns.glEnd ();
      renderer->set_polygon_offset (false);
    }

    void vertex (void *data)
    {
      opengl_functions& glfcns = renderer->get_opengl_functions ();

      vertex_data::vertex_data_rep *v
        = reinterpret_cast<vertex_data::vertex_data_rep *> (data);
      //printf ("patch_tessellator::vertex (%g, %g, %g)\n", v->coords(0), v->coords(1), v->coords(2));

      // NOTE: OpenGL can re-order vertices.  For "flat" coloring of FaceColor
      // the first vertex must be identified in the draw_patch routine.

      if (color_mode == INTERP || (color_mode == FLAT && ! is_filled ()))
        {
          Matrix col = v->color;

          if (col.numel () == 3)
            {
              glfcns.glColor4d (col(0), col(1), col(2), v->alpha);
              if (light_mode > 0)
                {
                  // edge lighting only uses ambient light
                  float buf[4] = { 0.0f, 0.0f, 0.0f, 1.0f };;

                  if (face_lighting)
                    for (int k = 0; k < 3; k++)
                      buf[k] = v->specular * (v->specular_color_refl +
                                              (1 - v->specular_color_refl) * col(k));
                  glfcns.glMaterialfv (LIGHT_MODE, GL_SPECULAR, buf);

                  if (face_lighting)
                    for (int k = 0; k < 3; k++)
                      buf[k] = (v->diffuse * col(k));
                  glfcns.glMaterialfv (LIGHT_MODE, GL_DIFFUSE, buf);

                  for (int k = 0; k < 3; k++)
                    buf[k] = (v->ambient * col(k));
                  glfcns.glMaterialfv (LIGHT_MODE, GL_AMBIENT, buf);
                }
            }
        }

      if (light_mode == FLAT && first)
        glfcns.glNormal3dv (v->face_normal.data ());
      else if (light_mode == GOURAUD)
        glfcns.glNormal3dv (v->vertex_normal.data ());

      glfcns.glVertex3dv (v->coords.data ());

      first = false;
    }

    void combine (GLdouble xyz[3], void *data[4], GLfloat w[4], void **out_data)
    {
      //printf ("patch_tessellator::combine\n");

      vertex_data::vertex_data_rep *v[4];
      int vmax = 4;

      for (int i = 0; i < 4; i++)
        {
          v[i] = reinterpret_cast<vertex_data::vertex_data_rep *> (data[i]);

          if (vmax == 4 && ! v[i])
            vmax = i;
        }

      Matrix vv (1, 3, 0.0);
      Matrix cc;
      Matrix vnn (1, 3, 0.0);
      Matrix fnn (1, 3, 0.0);
      double aa = 0.0;

      vv(0) = xyz[0];
      vv(1) = xyz[1];
      vv(2) = xyz[2];

      if (v[0]->color.numel ())
        {
          cc.resize (1, 3, 0.0);
          for (int ic = 0; ic < 3; ic++)
            for (int iv = 0; iv < vmax; iv++)
              cc(ic) += (w[iv] * v[iv]->color (ic));
        }

      if (v[0]->vertex_normal.numel () > 0)
        {
          for (int in = 0; in < 3; in++)
            for (int iv = 0; iv < vmax; iv++)
              vnn(in) += (w[iv] * v[iv]->vertex_normal (in));
        }

      if (v[0]->face_normal.numel () > 0)
        {
          for (int in = 0; in < 3; in++)
            for (int iv = 0; iv < vmax; iv++)
              fnn(in) += (w[iv] * v[iv]->face_normal (in));
        }

      for (int iv = 0; iv < vmax; iv++)
        aa += (w[iv] * v[iv]->alpha);

      vertex_data new_v (vv, cc, vnn, fnn, aa, v[0]->ambient, v[0]->diffuse,
                         v[0]->specular, v[0]->specular_exp,
                         v[0]->specular_color_refl);
      tmp_vdata.push_back (new_v);

      *out_data = new_v.get_rep ();
    }

  private:

    // No copying!

    patch_tessellator (const patch_tessellator&) = delete;

    patch_tessellator& operator = (const patch_tessellator&) = delete;

    opengl_renderer *renderer;
    int color_mode;
    int light_mode;
    bool face_lighting;
    int index;
    bool first;
    std::list<vertex_data> tmp_vdata;
  };

#else

  class
  opengl_renderer::patch_tessellator
  {
    // Dummy class.
  };

#endif

  opengl_renderer::opengl_renderer (opengl_functions& glfcns)
    : m_glfcns (glfcns), xmin (), xmax (), ymin (), ymax (), zmin (), zmax (),
      m_devpixratio (1.0), xform (), toolkit (), xZ1 (), xZ2 (), marker_id (),
      filled_marker_id (), camera_pos (), camera_dir (), view_vector (),
      interpreter ("none"), txt_renderer (), m_current_light (0),
      m_max_lights (0), selecting (false), m_printing (false)
  {
    // This constructor will fail if we don't have OpenGL or if the data
    // types we assumed in our public interface aren't compatible with the
    // OpenGL types.

#if defined (HAVE_OPENGL)

    // Ensure that we can't request an image larger than OpenGL can handle.
    // FIXME: should we check signed vs. unsigned?

    static bool ok = (sizeof (int) <= sizeof (GLsizei));

    if (! ok)
      error ("the size of GLsizei is smaller than the size of int");

#else

    err_disabled_feature ("opengl_renderer", "OpenGL");

#endif
  }

  void
  opengl_renderer::draw (const graphics_object& go, bool toplevel)
  {
    if (! go.valid_object ())
      return;

    const base_properties& props = go.get_properties ();

    if (! toolkit)
      toolkit = props.get_toolkit ();

    if (go.isa ("figure"))
      draw_figure (dynamic_cast<const figure::properties&> (props));
    else if (go.isa ("axes"))
      draw_axes (dynamic_cast<const axes::properties&> (props));
    else if (go.isa ("line"))
      draw_line (dynamic_cast<const line::properties&> (props));
    else if (go.isa ("surface"))
      draw_surface (dynamic_cast<const surface::properties&> (props));
    else if (go.isa ("patch"))
      draw_patch (dynamic_cast<const patch::properties&> (props));
    else if (go.isa ("light"))
      draw_light (dynamic_cast<const light::properties&> (props));
    else if (go.isa ("hggroup"))
      draw_hggroup (dynamic_cast<const hggroup::properties&> (props));
    else if (go.isa ("text"))
      draw_text (dynamic_cast<const text::properties&> (props));
    else if (go.isa ("image"))
      draw_image (dynamic_cast<const image::properties&> (props));
    else if (go.isa ("uimenu") || go.isa ("uicontrol")
             || go.isa ("uicontextmenu") || go.isa ("uitoolbar")
             || go.isa ("uipushtool") || go.isa ("uitoggletool")
             || go.isa ("uitable"))
      ; // SKIP
    else if (go.isa ("uipanel"))
      {
        if (toplevel)
          draw_uipanel (dynamic_cast<const uipanel::properties&> (props), go);
      }
    else if (go.isa ("uibuttongroup"))
      {
        if (toplevel)
          draw_uibuttongroup (dynamic_cast<const uibuttongroup::properties&> (props), go);
      }
    else
      {
        warning ("opengl_renderer: cannot render object of type '%s'",
                 props.graphics_object_name ().c_str ());
      }

#if defined (HAVE_OPENGL)

    GLenum gl_error = m_glfcns.glGetError ();
    if (gl_error)
      warning ("opengl_renderer: Error '%s' (%d) occurred drawing '%s' object",
               gluErrorString (gl_error), gl_error, props.graphics_object_name ().c_str ());

#endif
  }

  void
  opengl_renderer::draw_figure (const figure::properties& props)
  {
    m_printing = props.is___printing__ ();

    // Initialize OpenGL context
    init_gl_context (props.is_graphicssmoothing (), props.get_color_rgb ());

#if defined (HAVE_OPENGL)

    props.set___gl_extensions__ (get_string (GL_EXTENSIONS));
    props.set___gl_renderer__ (get_string (GL_RENDERER));
    props.set___gl_vendor__ (get_string (GL_VENDOR));
    props.set___gl_version__ (get_string (GL_VERSION));

#endif

    // Draw children

    draw (props.get_all_children (), false);
  }

  void
  opengl_renderer::draw_uipanel (const uipanel::properties& props,
                                 const graphics_object& go)
  {
    graphics_object fig = go.get_ancestor ("figure");
    const figure::properties& figProps
      = dynamic_cast<const figure::properties&> (fig.get_properties ());

    // Initialize OpenGL context

    init_gl_context (figProps.is_graphicssmoothing (),
                     props.get_backgroundcolor_rgb ());

    // Draw children

    draw (props.get_all_children (), false);
  }

  void
  opengl_renderer::draw_uibuttongroup (const uibuttongroup::properties& props,
                                       const graphics_object& go)
  {
    graphics_object fig = go.get_ancestor ("figure");
    const figure::properties& figProps
      = dynamic_cast<const figure::properties&> (fig.get_properties ());

    // Initialize OpenGL context

    init_gl_context (figProps.is_graphicssmoothing (),
                     props.get_backgroundcolor_rgb ());

    // Draw children

    draw (props.get_all_children (), false);
  }

  void
  opengl_renderer::init_gl_context (bool enhanced, const Matrix& c)
  {
#if defined (HAVE_OPENGL)

    // Initialize OpenGL context

    m_glfcns.glEnable (GL_DEPTH_TEST);
    m_glfcns.glDepthFunc (GL_LEQUAL);
    m_glfcns.glBlendFunc (GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
    m_glfcns.glAlphaFunc (GL_GREATER, 0.0f);
    m_glfcns.glEnable (GL_NORMALIZE);
    m_glfcns.glEnable (GL_BLEND);

    if (enhanced)
      {
        m_glfcns.glEnable (GL_MULTISAMPLE);
        bool has_multisample = false;
        if (! m_glfcns.glGetError ())
          {
            GLint iMultiSample, iNumSamples;
            m_glfcns.glGetIntegerv (GL_SAMPLE_BUFFERS, &iMultiSample);
            m_glfcns.glGetIntegerv (GL_SAMPLES, &iNumSamples);
            if (iMultiSample == GL_TRUE && iNumSamples > 0)
              has_multisample = true;
          }

        if (! has_multisample)
          {
            // MultiSample not implemented.  Use old-style anti-aliasing
            m_glfcns.glDisable (GL_MULTISAMPLE);
            // Disabling GL_MULTISAMPLE will raise a gl error if it is not
            // implemented.  Thus, call glGetError to reset the error state.
            m_glfcns.glGetError ();

            m_glfcns.glEnable (GL_LINE_SMOOTH);
            m_glfcns.glHint (GL_LINE_SMOOTH_HINT, GL_NICEST);
          }
      }
    else
      {
        m_glfcns.glDisable (GL_LINE_SMOOTH);
      }

    // Clear background

    if (c.numel () >= 3)
      {
        m_glfcns.glClearColor (c(0), c(1), c(2), 1);
        m_glfcns.glClear (GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
      }

    GLenum gl_error = m_glfcns.glGetError ();
    if (gl_error)
      warning ("opengl_renderer: Error '%s' (%d) occurred in init_gl_context",
               gluErrorString (gl_error), gl_error);

#else

    octave_unused_parameter (enhanced);
    octave_unused_parameter (c);

    // This shouldn't happen because construction of opengl_renderer
    // objects is supposed to be impossible if OpenGL is not available.

    panic_impossible ();

#endif
  }

  void
  opengl_renderer::render_grid (const double linewidth,
                                const std::string& gridstyle,
                                const Matrix& gridcolor, const double gridalpha,
                                const Matrix& ticks, double lim1, double lim2,
                                double p1, double p1N, double p2, double p2N,
                                int xyz, bool is_3D)
  {
#if defined (HAVE_OPENGL)

    m_glfcns.glColor4d (gridcolor(0), gridcolor(1), gridcolor(2), gridalpha);
    set_linestyle (gridstyle, true, linewidth);
    m_glfcns.glBegin (GL_LINES);
    for (int i = 0; i < ticks.numel (); i++)
      {
        double val = ticks(i);
        if (lim1 <= val && val <= lim2)
          {
            if (xyz == X_AXIS)
              {
                m_glfcns.glVertex3d (val, p1N, p2);
                m_glfcns.glVertex3d (val, p1, p2);
                if (is_3D)
                  {
                    m_glfcns.glVertex3d (val, p1, p2N);
                    m_glfcns.glVertex3d (val, p1, p2);
                  }
              }
            else if (xyz == Y_AXIS)
              {
                m_glfcns.glVertex3d (p1N, val, p2);
                m_glfcns.glVertex3d (p1, val, p2);
                if (is_3D)
                  {
                    m_glfcns.glVertex3d (p1, val, p2N);
                    m_glfcns.glVertex3d (p1, val, p2);
                  }
              }
            else if (xyz == Z_AXIS)
              {
                m_glfcns.glVertex3d (p1N, p2, val);
                m_glfcns.glVertex3d (p1, p2, val);
                m_glfcns.glVertex3d (p1, p2N, val);
                m_glfcns.glVertex3d (p1, p2, val);
              }
          }
      }
    m_glfcns.glEnd ();
    set_linestyle ("-");  // Disable LineStipple
    double black[3] = {0, 0, 0};
    m_glfcns.glColor3dv (black);

#else

    octave_unused_parameter (linewidth);
    octave_unused_parameter (gridstyle);
    octave_unused_parameter (gridcolor);
    octave_unused_parameter (gridalpha);
    octave_unused_parameter (ticks);
    octave_unused_parameter (lim1);
    octave_unused_parameter (lim2);
    octave_unused_parameter (p1);
    octave_unused_parameter (p1N);
    octave_unused_parameter (p2);
    octave_unused_parameter (p2N);
    octave_unused_parameter (xyz);
    octave_unused_parameter (is_3D);

    // This shouldn't happen because construction of opengl_renderer
    // objects is supposed to be impossible if OpenGL is not available.

    panic_impossible ();

#endif
  }

  void
  opengl_renderer::render_tickmarks (const Matrix& ticks,
                                     double lim1, double lim2,
                                     double p1, double p1N,
                                     double p2, double p2N,
                                     double dx, double dy, double dz,
                                     int xyz, bool mirror)
  {
#if defined (HAVE_OPENGL)

    m_glfcns.glBegin (GL_LINES);

    for (int i = 0; i < ticks.numel (); i++)
      {
        double val = ticks(i);

        if (lim1 <= val && val <= lim2)
          {
            if (xyz == X_AXIS)
              {
                m_glfcns.glVertex3d (val, p1, p2);
                m_glfcns.glVertex3d (val, p1+dy, p2+dz);
                if (mirror)
                  {
                    m_glfcns.glVertex3d (val, p1N, p2N);
                    m_glfcns.glVertex3d (val, p1N-dy, p2N-dz);
                  }
              }
            else if (xyz == Y_AXIS)
              {
                m_glfcns.glVertex3d (p1, val, p2);
                m_glfcns.glVertex3d (p1+dx, val, p2+dz);
                if (mirror)
                  {
                    m_glfcns.glVertex3d (p1N, val, p2N);
                    m_glfcns.glVertex3d (p1N-dx, val, p2N-dz);
                  }
              }
            else if (xyz == Z_AXIS)
              {
                m_glfcns.glVertex3d (p1, p2, val);
                m_glfcns.glVertex3d (p1+dx, p2+dy, val);
                if (mirror)
                  {
                    m_glfcns.glVertex3d (p1N, p2N, val);
                    m_glfcns.glVertex3d (p1N-dx, p2N-dy, val);
                  }
              }
          }
      }

    m_glfcns.glEnd ();

#else

    octave_unused_parameter (ticks);
    octave_unused_parameter (lim1);
    octave_unused_parameter (lim2);
    octave_unused_parameter (p1);
    octave_unused_parameter (p1N);
    octave_unused_parameter (p2);
    octave_unused_parameter (p2N);
    octave_unused_parameter (dx);
    octave_unused_parameter (dy);
    octave_unused_parameter (dz);
    octave_unused_parameter (xyz);
    octave_unused_parameter (mirror);

    // This shouldn't happen because construction of opengl_renderer
    // objects is supposed to be impossible if OpenGL is not available.

    panic_impossible ();

#endif
  }

  void
  opengl_renderer::render_ticktexts (const Matrix& ticks,
                                     const string_vector& ticklabels,
                                     double lim1, double lim2,
                                     double p1, double p2,
                                     int xyz, int ha, int va,
                                     int& wmax, int& hmax)
  {
#if defined (HAVE_OPENGL)

    int nticks  = ticks.numel ();
    int nlabels = ticklabels.numel ();

    if (nlabels == 0)
      return;

    for (int i = 0; i < nticks; i++)
      {
        double val = ticks(i);

        if (lim1 <= val && val <= lim2)
          {
            Matrix b;

            std::string label (ticklabels(i % nlabels));
            label.erase (0, label.find_first_not_of (' '));
            label = label.substr (0, label.find_last_not_of (' ')+1);

            // FIXME: As tick text is transparent, shouldn't it be
            //        drawn after axes object, for correct rendering?
            if (xyz == X_AXIS)
              {
                b = render_text (label, val, p1, p2, ha, va);
              }
            else if (xyz == Y_AXIS)
              {
                b = render_text (label, p1, val, p2, ha, va);
              }
            else if (xyz == Z_AXIS)
              {
                b = render_text (label, p1, p2, val, ha, va);
              }

            wmax = std::max (wmax, static_cast<int> (b(2)));
            hmax = std::max (hmax, static_cast<int> (b(3)));
          }
      }

#else

    octave_unused_parameter (ticks);
    octave_unused_parameter (ticklabels);
    octave_unused_parameter (lim1);
    octave_unused_parameter (lim2);
    octave_unused_parameter (p1);
    octave_unused_parameter (p2);
    octave_unused_parameter (xyz);
    octave_unused_parameter (ha);
    octave_unused_parameter (va);
    octave_unused_parameter (wmax);
    octave_unused_parameter (hmax);

    // This shouldn't happen because construction of opengl_renderer
    // objects is supposed to be impossible if OpenGL is not available.

    panic_impossible ();

#endif
  }

  void
  opengl_renderer::draw_zoom_rect (int x1, int y1, int x2, int y2)
  {
#if defined (HAVE_OPENGL)

    m_glfcns.glVertex2d (x1, y1);
    m_glfcns.glVertex2d (x2, y1);
    m_glfcns.glVertex2d (x2, y2);
    m_glfcns.glVertex2d (x1, y2);
    m_glfcns.glVertex2d (x1, y1);

#else

    octave_unused_parameter (x1);
    octave_unused_parameter (x2);
    octave_unused_parameter (y1);
    octave_unused_parameter (y2);

    // This shouldn't happen because construction of opengl_renderer
    // objects is supposed to be impossible if OpenGL is not available.

    panic_impossible ();

#endif
  }

  void
  opengl_renderer::draw_zoom_box (int width, int height,
                                  int x1, int y1, int x2, int y2,
                                  const Matrix& overlaycolor,
                                  double overlayalpha,
                                  const Matrix& bordercolor,
                                  double borderalpha, double borderwidth)
  {
#if defined (HAVE_OPENGL)

    m_glfcns.glMatrixMode (GL_MODELVIEW);
    m_glfcns.glPushMatrix ();
    m_glfcns.glLoadIdentity ();

    m_glfcns.glMatrixMode (GL_PROJECTION);
    m_glfcns.glPushMatrix ();
    m_glfcns.glLoadIdentity ();
    m_glfcns.glOrtho (0, width, height, 0, 1, -1);

    m_glfcns.glPushAttrib (GL_DEPTH_BUFFER_BIT | GL_CURRENT_BIT);
    m_glfcns.glDisable (GL_DEPTH_TEST);

    m_glfcns.glBegin (GL_POLYGON);
    m_glfcns.glColor4f (overlaycolor(0), overlaycolor(1), overlaycolor(2),
                        overlayalpha);
    draw_zoom_rect (x1, y1, x2, y2);
    m_glfcns.glEnd ();

    m_glfcns.glLineWidth (borderwidth);
    m_glfcns.glBegin (GL_LINE_STRIP);
    m_glfcns.glColor4f (bordercolor(0), bordercolor(1), bordercolor(2),
                        borderalpha);
    draw_zoom_rect (x1, y1, x2, y2);
    m_glfcns.glEnd ();

    m_glfcns.glPopAttrib ();

    m_glfcns.glMatrixMode (GL_MODELVIEW);
    m_glfcns.glPopMatrix ();

    m_glfcns.glMatrixMode (GL_PROJECTION);
    m_glfcns.glPopMatrix ();

#else

    octave_unused_parameter (width);
    octave_unused_parameter (height);
    octave_unused_parameter (x1);
    octave_unused_parameter (x2);
    octave_unused_parameter (y1);
    octave_unused_parameter (y2);
    octave_unused_parameter (overlaycolor);
    octave_unused_parameter (overlayalpha);
    octave_unused_parameter (bordercolor);
    octave_unused_parameter (borderalpha);
    octave_unused_parameter (borderwidth);

    // This shouldn't happen because construction of opengl_renderer
    // objects is supposed to be impossible if OpenGL is not available.

    panic_impossible ();

#endif
  }

  uint8NDArray
  opengl_renderer::get_pixels (int width, int height)
  {
#if defined (HAVE_OPENGL)

    m_glfcns.glPixelStorei (GL_PACK_ALIGNMENT, 1);
    uint8NDArray pix(dim_vector (3, width, height), 0);

    m_glfcns.glReadPixels(0, 0, width, height, GL_RGB, GL_UNSIGNED_BYTE,
                          pix.fortran_vec ());

    // Permute and flip data
    Array<octave_idx_type> perm (dim_vector (3, 1));
    perm(0) = 2;
    perm(1) = 1;
    perm(2) = 0;

    Array<idx_vector> idx (dim_vector (3, 1));
    idx(0) = idx_vector::make_range (height - 1, -1, height);
    idx(1) = idx_vector::colon;
    idx(2) = idx_vector::colon;

    return pix.permute (perm).index (idx);

#else

    // This shouldn't happen because construction of opengl_renderer
    // objects is supposed to be impossible if OpenGL is not available.

    octave_unused_parameter (width);
    octave_unused_parameter (height);

    panic_impossible ();

#endif
  }

  void
  opengl_renderer::finish (void)
  {
#if defined (HAVE_OPENGL)

    m_glfcns.glFinish ();

#else

    // This shouldn't happen because construction of opengl_renderer
    // objects is supposed to be impossible if OpenGL is not available.

    panic_impossible ();

#endif
  }

  void
  opengl_renderer::setup_opengl_transformation (const axes::properties& props)
  {
#if defined (HAVE_OPENGL)

    // setup OpenGL transformation

    Matrix x_zlim = props.get_transform_zlim ();

    xZ1 = std::max (-1e6, x_zlim(0)-(x_zlim(1)-x_zlim(0))*100.0);
    xZ2 = std::min (1e6, x_zlim(1)+(x_zlim(1)-x_zlim(0))*100.0);

    Matrix x_mat1 = props.get_opengl_matrix_1 ();
    Matrix x_mat2 = props.get_opengl_matrix_2 ();

    m_glfcns.glMatrixMode (GL_MODELVIEW);
    m_glfcns.glLoadIdentity ();
    m_glfcns.glScaled (1, 1, -1);
    m_glfcns.glMultMatrixd (x_mat1.data ());
    m_glfcns.glMatrixMode (GL_PROJECTION);
    m_glfcns.glLoadIdentity ();

    Matrix vp = get_viewport_scaled ();
    m_glfcns.glOrtho (0, vp(2), vp(3), 0, xZ1, xZ2);
    m_glfcns.glMultMatrixd (x_mat2.data ());
    m_glfcns.glMatrixMode (GL_MODELVIEW);

    m_glfcns.glClear (GL_DEPTH_BUFFER_BIT);

    // store axes transformation data

    xform = props.get_transform ();

#else

    octave_unused_parameter (props);

    // This shouldn't happen because construction of opengl_renderer
    // objects is supposed to be impossible if OpenGL is not available.

    panic_impossible ();

#endif
  }

  void
  opengl_renderer::draw_axes_planes (const axes::properties& props)
  {
#if defined (HAVE_OPENGL)

    Matrix axe_color = props.get_color_rgb ();
    if (axe_color.isempty () || ! props.is_visible ())
      return;

    double xPlane = props.get_xPlane ();
    double yPlane = props.get_yPlane ();
    double zPlane = props.get_zPlane ();
    double xPlaneN = props.get_xPlaneN ();
    double yPlaneN = props.get_yPlaneN ();
    double zPlaneN = props.get_zPlaneN ();
    bool is2D = props.get_is2D ();

    // Axes planes
    set_color (axe_color);
    set_polygon_offset (true, 9.0);

    m_glfcns.glBegin (GL_QUADS);

    if (! is2D)
      {
        // X plane
        m_glfcns.glVertex3d (xPlane, yPlaneN, zPlaneN);
        m_glfcns.glVertex3d (xPlane, yPlane, zPlaneN);
        m_glfcns.glVertex3d (xPlane, yPlane, zPlane);
        m_glfcns.glVertex3d (xPlane, yPlaneN, zPlane);

        // Y plane
        m_glfcns.glVertex3d (xPlaneN, yPlane, zPlaneN);
        m_glfcns.glVertex3d (xPlane, yPlane, zPlaneN);
        m_glfcns.glVertex3d (xPlane, yPlane, zPlane);
        m_glfcns.glVertex3d (xPlaneN, yPlane, zPlane);
      }

    // Z plane
    m_glfcns.glVertex3d (xPlaneN, yPlaneN, zPlane);
    m_glfcns.glVertex3d (xPlane, yPlaneN, zPlane);
    m_glfcns.glVertex3d (xPlane, yPlane, zPlane);
    m_glfcns.glVertex3d (xPlaneN, yPlane, zPlane);

    m_glfcns.glEnd ();

    set_polygon_offset (false);

#else

    octave_unused_parameter (props);

    // This shouldn't happen because construction of opengl_renderer
    // objects is supposed to be impossible if OpenGL is not available.

    panic_impossible ();

#endif
  }

  void
  opengl_renderer::draw_axes_boxes (const axes::properties& props)
  {
#if defined (HAVE_OPENGL)

    if (! props.is_visible ())
      return;

    bool xySym = props.get_xySym ();
    bool layer2Dtop = props.get_layer2Dtop ();
    bool is2D = props.get_is2D ();
    bool isXOrigin = props.xaxislocation_is ("origin")
                     && ! props.yscale_is ("log");
    bool isYOrigin = props.yaxislocation_is ("origin")
                     && ! props.xscale_is ("log");
    bool boxFull = (props.get_boxstyle () == "full");
    double linewidth = props.get_linewidth ();
    double xPlane = props.get_xPlane ();
    double yPlane = props.get_yPlane ();
    double zPlane = props.get_zPlane ();
    double xPlaneN = props.get_xPlaneN ();
    double yPlaneN = props.get_yPlaneN ();
    double zPlaneN = props.get_zPlaneN ();
    double xpTick = props.get_xpTick ();
    double ypTick = props.get_ypTick ();
    double zpTick = props.get_zpTick ();
    double xpTickN = props.get_xpTickN ();
    double ypTickN = props.get_ypTickN ();
    double zpTickN = props.get_zpTickN ();

    bool plotyy = (props.has_property ("__plotyy_axes__"));

    // Axes box

    set_linecap ("square");
    set_linestyle ("-", true, linewidth);

    m_glfcns.glBegin (GL_LINES);

    if (layer2Dtop)
      std::swap (zpTick, zpTickN);

    // X box
    Matrix color = props.get_xcolor_rgb ();

    if (! color.isempty ())
      {
        set_color (color);

        if (! isXOrigin || props.is_box() || ! is2D)
          {
            m_glfcns.glVertex3d (xPlaneN, ypTick, zpTick);
            m_glfcns.glVertex3d (xPlane, ypTick, zpTick);
          }

        if (props.is_box ())
          {
            m_glfcns.glVertex3d (xPlaneN, ypTickN, zpTick);
            m_glfcns.glVertex3d (xPlane, ypTickN, zpTick);
            if (! is2D)
              {
                m_glfcns.glVertex3d (xPlaneN, ypTickN, zpTickN);
                m_glfcns.glVertex3d (xPlane, ypTickN, zpTickN);
                if (boxFull)
                  {
                    m_glfcns.glVertex3d (xPlaneN, ypTick, zpTickN);
                    m_glfcns.glVertex3d (xPlane, ypTick, zpTickN);
                  }
              }
          }
      }

    // Y box
    color = props.get_ycolor_rgb ();

    if (! color.isempty ())
      {
        set_color (color);
        if (! isYOrigin || props.is_box() || ! is2D)
          {
            m_glfcns.glVertex3d (xpTick, yPlaneN, zpTick);
            m_glfcns.glVertex3d (xpTick, yPlane, zpTick);
          }

        if (props.is_box () && ! plotyy)
          {
            m_glfcns.glVertex3d (xpTickN, yPlaneN, zpTick);
            m_glfcns.glVertex3d (xpTickN, yPlane, zpTick);

            if (! is2D)
              {
                m_glfcns.glVertex3d (xpTickN, yPlaneN, zpTickN);
                m_glfcns.glVertex3d (xpTickN, yPlane, zpTickN);
                if (boxFull)
                  {
                    m_glfcns.glVertex3d (xpTick, yPlaneN, zpTickN);
                    m_glfcns.glVertex3d (xpTick, yPlane, zpTickN);
                  }
              }
          }
      }

    // Z box
    color = props.get_zcolor_rgb ();

    if (! color.isempty () && ! is2D)
      {
        set_color (color);

        if (xySym)
          {
            m_glfcns.glVertex3d (xPlaneN, yPlane, zPlaneN);
            m_glfcns.glVertex3d (xPlaneN, yPlane, zPlane);
          }
        else
          {
            m_glfcns.glVertex3d (xPlane, yPlaneN, zPlaneN);
            m_glfcns.glVertex3d (xPlane, yPlaneN, zPlane);
          }

        if (props.is_box ())
          {
            m_glfcns.glVertex3d (xPlane, yPlane, zPlaneN);
            m_glfcns.glVertex3d (xPlane, yPlane, zPlane);

            if (xySym)
              {
                m_glfcns.glVertex3d (xPlane, yPlaneN, zPlaneN);
                m_glfcns.glVertex3d (xPlane, yPlaneN, zPlane);
              }
            else
              {
                m_glfcns.glVertex3d (xPlaneN, yPlane, zPlaneN);
                m_glfcns.glVertex3d (xPlaneN, yPlane, zPlane);
              }

            if (boxFull)
              {
                m_glfcns.glVertex3d (xPlaneN, yPlaneN, zPlaneN);
                m_glfcns.glVertex3d (xPlaneN, yPlaneN, zPlane);
              }
          }
      }

    m_glfcns.glEnd ();

    set_linestyle ("-");  // Disable LineStipple

#else

    octave_unused_parameter (props);

    // This shouldn't happen because construction of opengl_renderer
    // objects is supposed to be impossible if OpenGL is not available.

    panic_impossible ();

#endif
  }

  void
  opengl_renderer::draw_axes_x_grid (const axes::properties& props)
  {
#if defined (HAVE_OPENGL)

    gh_manager& gh_mgr
      = __get_gh_manager__ ("opengl_renderer::draw_axes_x_grid");

    int xstate = props.get_xstate ();

    if (xstate != AXE_DEPTH_DIR
        && (props.is_visible ()
            || (selecting && props.pickableparts_is ("all"))))
      {
        int zstate = props.get_zstate ();
        bool x2Dtop = props.get_x2Dtop ();
        bool layer2Dtop = props.get_layer2Dtop ();
        bool xyzSym = props.get_xyzSym ();
        bool nearhoriz = props.get_nearhoriz ();
        double xticklen = props.get_xticklen ();
        double xtickoffset = props.get_xtickoffset ();
        double fy = props.get_fy ();
        double fz = props.get_fz ();
        double x_min = props.get_x_min ();
        double x_max = props.get_x_max ();
        double y_min = props.get_y_min ();
        double y_max = props.get_y_max ();
        double yPlane = props.get_yPlane ();
        double yPlaneN = props.get_yPlaneN ();
        double ypTick = props.get_ypTick ();
        double ypTickN = props.get_ypTickN ();
        double zPlane = props.get_zPlane ();
        double zPlaneN = props.get_zPlaneN ();
        double zpTick = props.get_zpTick ();
        double zpTickN = props.get_zpTickN ();

        // X ticks and grid properties
        Matrix xticks = xform.xscale (props.get_xtick ().matrix_value ());
        Matrix xmticks = xform.xscale (props.get_xminortickvalues ().matrix_value ());
        bool do_xminortick = props.is_xminortick () && ! xticks.isempty ();
        string_vector xticklabels = props.get_xticklabel ().string_vector_value ();
        int wmax = 0;
        int hmax = 0;
        bool tick_along_z = nearhoriz || math::isinf (fy);
        double linewidth = props.get_linewidth ();
        std::string gridstyle = props.get_gridlinestyle ();
        std::string minorgridstyle = props.get_minorgridlinestyle ();
        Matrix gridcolor = props.get_gridcolor_rgb ();
        Matrix minorgridcolor = props.get_minorgridcolor_rgb ();
        double gridalpha = props.get_gridalpha ();
        double minorgridalpha = props.get_minorgridalpha ();
        bool do_xgrid = (props.is_xgrid () && (gridstyle != "none"));
        bool do_xminorgrid = (props.is_xminorgrid ()
                              && (minorgridstyle != "none")
                              && ! xticks.isempty ());
        bool is_origin = props.xaxislocation_is ("origin") && props.get_is2D ()
                         && ! props.yscale_is ("log");
        bool is_origin_low = is_origin && (y_min + y_max) < 0;
        bool mirror = props.is_box () && xstate != AXE_ANY_DIR;

        // X grid

        // possibly use axis color for gridcolor & minorgridcolor
        if (props.gridcolormode_is ("auto"))
          if (props.xcolormode_is ("manual") && ! props.xcolor_is ("none"))
            gridcolor = props.get_xcolor_rgb ();

        if (props.minorgridcolormode_is ("auto"))
          if (props.xcolormode_is ("manual") && ! props.xcolor_is ("none"))
            minorgridcolor = props.get_xcolor_rgb ();

        if (gridcolor.isempty ())
          do_xgrid = false;

        if (minorgridcolor.isempty ())
          do_xminorgrid = false;

        // set styles when drawing only minor grid
        if (do_xminorgrid && ! do_xgrid)
          {
            gridstyle = minorgridstyle;
            gridcolor = minorgridcolor;
            gridalpha = minorgridalpha;
            do_xgrid = true;
          }

        // minor grid lines
        if (do_xminorgrid)
          render_grid (linewidth,
                       minorgridstyle, minorgridcolor, minorgridalpha,
                       xmticks, x_min, x_max,
                       yPlane, yPlaneN, layer2Dtop ? zPlaneN : zPlane, zPlaneN,
                       0, (zstate != AXE_DEPTH_DIR));

        // grid lines
        if (do_xgrid)
          render_grid (linewidth,
                       gridstyle, gridcolor, gridalpha,
                       xticks, x_min, x_max,
                       yPlane, yPlaneN, layer2Dtop ? zPlaneN : zPlane, zPlaneN,
                       0, (zstate != AXE_DEPTH_DIR));

        // Skip drawing axis, ticks, and ticklabels when color is "none"
        if (props.xcolor_is ("none"))
          return;

        set_color (props.get_xcolor_rgb ());

        // axis line
        double y_axis_pos = 0.;
        if (is_origin)
          {
            y_axis_pos = math::max (math::min (0., y_max), y_min);
            m_glfcns.glBegin (GL_LINES);
            set_color (props.get_xcolor_rgb ());
            m_glfcns.glVertex3d (x_min, y_axis_pos, zpTick);
            m_glfcns.glVertex3d (x_max, y_axis_pos, zpTick);
            m_glfcns.glEnd ();
          }

        // minor tick marks
        if (do_xminortick)
          {
            if (tick_along_z)
              render_tickmarks (xmticks, x_min, x_max,
                                is_origin ? y_axis_pos : ypTick, ypTick,
                                zpTick, zpTickN, 0., 0.,
                                (is_origin_low ? -1. : 1.) *
                                math::signum (zpTick-zpTickN)*fz*xticklen/2,
                                0, ! is_origin && mirror);
            else
              render_tickmarks (xmticks, x_min, x_max,
                                is_origin ? y_axis_pos : ypTick, ypTickN,
                                zpTick, zpTick, 0.,
                                (is_origin_low ? -1. : 1.) *
                                math::signum (ypTick-ypTickN)*fy*xticklen/2,
                                0., 0, ! is_origin && mirror);
          }

        // tick marks
        if (tick_along_z)
          render_tickmarks (xticks, x_min, x_max,
                            is_origin ? y_axis_pos : ypTick, ypTick,
                            zpTick, zpTickN, 0., 0.,
                            (is_origin_low ? -1. : 1.) *
                            math::signum (zpTick-zpTickN)*fz*xticklen,
                            0, ! is_origin && mirror);
        else
          render_tickmarks (xticks, x_min, x_max,
                            is_origin ? y_axis_pos : ypTick, ypTickN,
                            zpTick, zpTick, 0.,
                            (is_origin_low ? -1. : 1.) *
                            math::signum (ypTick-ypTickN)*fy*xticklen,
                            0., 0, ! is_origin && mirror);

        // tick texts
        if (xticklabels.numel () > 0)
          {
            int halign = (xstate == AXE_HORZ_DIR
                          ? 1
                          : (xyzSym || is_origin_low ? 0 : 2));
            int valign = (xstate == AXE_VERT_DIR
                          ? 1
                          : (x2Dtop || is_origin_low ? 0 : 2));

            if (tick_along_z)
              render_ticktexts (xticks, xticklabels, x_min, x_max,
                                is_origin ? y_axis_pos : ypTick,
                                zpTick +
                                (is_origin_low ? -1. : 1.) *
                                math::signum (zpTick-zpTickN)*fz*xtickoffset,
                                0, halign, valign, wmax, hmax);
            else
              render_ticktexts (xticks, xticklabels, x_min, x_max,
                                (is_origin ? y_axis_pos : ypTick) +
                                (is_origin_low ?  -1. : 1.) *
                                math::signum (ypTick-ypTickN)*fy*xtickoffset,
                                zpTick, 0, halign, valign, wmax, hmax);
          }

        gh_mgr.get_object (props.get_xlabel ()).set ("visible", "on");
      }
    else
      gh_mgr.get_object (props.get_xlabel ()).set ("visible", "off");

#else

    octave_unused_parameter (props);

    // This shouldn't happen because construction of opengl_renderer
    // objects is supposed to be impossible if OpenGL is not available.

    panic_impossible ();

#endif
  }

  void
  opengl_renderer::draw_axes_y_grid (const axes::properties& props)
  {
#if defined (HAVE_OPENGL)

    gh_manager& gh_mgr
      = __get_gh_manager__ ("opengl_renderer::draw_axes_y_grid");

    int ystate = props.get_ystate ();

    if (ystate != AXE_DEPTH_DIR && props.is_visible ()
        && (props.is_visible ()
            || (selecting && props.pickableparts_is ("all"))))
      {
        int zstate = props.get_zstate ();
        bool y2Dright = props.get_y2Dright ();
        bool layer2Dtop = props.get_layer2Dtop ();
        bool xyzSym = props.get_xyzSym ();
        bool nearhoriz = props.get_nearhoriz ();
        double yticklen = props.get_yticklen ();
        double ytickoffset = props.get_ytickoffset ();
        double fx = props.get_fx ();
        double fz = props.get_fz ();
        double xPlane = props.get_xPlane ();
        double xPlaneN = props.get_xPlaneN ();
        double xpTick = props.get_xpTick ();
        double xpTickN = props.get_xpTickN ();
        double y_min = props.get_y_min ();
        double y_max = props.get_y_max ();
        double x_min = props.get_x_min ();
        double x_max = props.get_x_max ();
        double zPlane = props.get_zPlane ();
        double zPlaneN = props.get_zPlaneN ();
        double zpTick = props.get_zpTick ();
        double zpTickN = props.get_zpTickN ();

        // Y ticks and grid properties
        Matrix yticks = xform.yscale (props.get_ytick ().matrix_value ());
        Matrix ymticks = xform.yscale (props.get_yminortickvalues ().matrix_value ());
        bool do_yminortick = props.is_yminortick () && ! yticks.isempty ();
        string_vector yticklabels = props.get_yticklabel ().string_vector_value ();
        int wmax = 0;
        int hmax = 0;
        bool tick_along_z = nearhoriz || math::isinf (fx);
        double linewidth = props.get_linewidth ();
        std::string gridstyle = props.get_gridlinestyle ();
        std::string minorgridstyle = props.get_minorgridlinestyle ();
        Matrix gridcolor = props.get_gridcolor_rgb ();
        Matrix minorgridcolor = props.get_minorgridcolor_rgb ();
        double gridalpha = props.get_gridalpha ();
        double minorgridalpha = props.get_minorgridalpha ();
        bool do_ygrid = (props.is_ygrid () && (gridstyle != "none"));
        bool do_yminorgrid = (props.is_yminorgrid ()
                              && (minorgridstyle != "none")
                              && ! yticks.isempty ());
        bool is_origin = props.yaxislocation_is ("origin") && props.get_is2D ()
                         && ! props.xscale_is ("log");
        bool is_origin_low = is_origin && (x_min + x_max) < 0;
        bool mirror = props.is_box () && ystate != AXE_ANY_DIR
                      && (! props.has_property ("__plotyy_axes__"));

        // Y grid

        // possibly use axis color for gridcolor & minorgridcolor
        if (props.gridcolormode_is ("auto"))
          if (props.ycolormode_is ("manual") && ! props.ycolor_is ("none"))
            gridcolor = props.get_ycolor_rgb ();

        if (props.minorgridcolormode_is ("auto"))
          if (props.ycolormode_is ("manual") && ! props.ycolor_is ("none"))
            minorgridcolor = props.get_ycolor_rgb ();

        if (gridcolor.isempty ())
          do_ygrid = false;

        if (minorgridcolor.isempty ())
          do_yminorgrid = false;

        // set styles when drawing only minor grid
        if (do_yminorgrid && ! do_ygrid)
          {
            gridstyle = minorgridstyle;
            gridcolor = minorgridcolor;
            gridalpha = minorgridalpha;
            do_ygrid = true;
          }

        // minor grid lines
        if (do_yminorgrid)
          render_grid (linewidth,
                       minorgridstyle, minorgridcolor, minorgridalpha,
                       ymticks, y_min, y_max,
                       xPlane, xPlaneN, layer2Dtop ? zPlaneN : zPlane, zPlaneN,
                       1, (zstate != AXE_DEPTH_DIR));

        // grid lines
        if (do_ygrid)
          render_grid (linewidth,
                       gridstyle, gridcolor, gridalpha,
                       yticks, y_min, y_max,
                       xPlane, xPlaneN, layer2Dtop ? zPlaneN : zPlane, zPlaneN,
                       1, (zstate != AXE_DEPTH_DIR));

        // Skip drawing axis, ticks, and ticklabels when color is "none"
        if (props.ycolor_is ("none"))
          return;

        set_color (props.get_ycolor_rgb ());

        // axis line
        double x_axis_pos = 0.;
        if (is_origin)
          {
            x_axis_pos = math::max (math::min (0., x_max), x_min);
            m_glfcns.glBegin (GL_LINES);
            set_color (props.get_ycolor_rgb ());
            m_glfcns.glVertex3d (x_axis_pos, y_min, zpTick);
            m_glfcns.glVertex3d (x_axis_pos, y_max, zpTick);
            m_glfcns.glEnd ();
          }

        // minor tick marks
        if (do_yminortick)
          {
            if (tick_along_z)
              render_tickmarks (ymticks, y_min, y_max,
                                is_origin ? x_axis_pos : xpTick, xpTick,
                                zpTick, zpTickN, 0., 0.,
                                (is_origin_low ? -1. : 1.) *
                                math::signum (zpTick-zpTickN)*fz*yticklen/2,
                                1, ! is_origin && mirror);
            else
              render_tickmarks (ymticks, y_min, y_max,
                                is_origin ? x_axis_pos : xpTick, xpTickN,
                                zpTick, zpTick,
                                (is_origin_low ? -1. : 1.) *
                                math::signum (xpTick-xpTickN)*fx*yticklen/2,
                                0., 0., 1, ! is_origin && mirror);
          }

        // tick marks
        if (tick_along_z)
          render_tickmarks (yticks, y_min, y_max,
                            is_origin ? x_axis_pos : xpTick, xpTick,
                            zpTick, zpTickN, 0., 0.,
                            (is_origin_low ? -1. : 1.) *
                            math::signum (zpTick-zpTickN)*fz*yticklen,
                            1, ! is_origin && mirror);
        else
          render_tickmarks (yticks, y_min, y_max,
                            is_origin ? x_axis_pos : xpTick, xpTickN,
                            zpTick, zpTick,
                            (is_origin_low ? -1. : 1.) *
                            math::signum (xPlaneN-xPlane)*fx*yticklen,
                            0., 0., 1, ! is_origin && mirror);

        // tick texts
        if (yticklabels.numel () > 0)
          {
            int halign = (ystate == AXE_HORZ_DIR
                          ? 1
                          : (! xyzSym || y2Dright || is_origin_low ? 0 : 2));
            int valign = (ystate == AXE_VERT_DIR
                          ? 1
                          : (is_origin_low ? 0 : 2));

            if (tick_along_z)
              render_ticktexts (yticks, yticklabels, y_min, y_max,
                                is_origin ? x_axis_pos : xpTick,
                                zpTick +
                                (is_origin_low ? -1. : 1.) *
                                math::signum (zpTick-zpTickN)*fz*ytickoffset,
                                1, halign, valign, wmax, hmax);
            else
              render_ticktexts (yticks, yticklabels, y_min, y_max,
                                (is_origin ? x_axis_pos : xpTick) +
                                (is_origin_low ?  -1. : 1.) *
                                math::signum (xpTick-xpTickN)*fx*ytickoffset,
                                zpTick, 1, halign, valign, wmax, hmax);
          }

        gh_mgr.get_object (props.get_ylabel ()).set ("visible", "on");
      }
    else
      gh_mgr.get_object (props.get_ylabel ()).set ("visible", "off");

#else

    octave_unused_parameter (props);

    // This shouldn't happen because construction of opengl_renderer
    // objects is supposed to be impossible if OpenGL is not available.

    panic_impossible ();

#endif
  }

  void
  opengl_renderer::draw_axes_z_grid (const axes::properties& props)
  {
    gh_manager& gh_mgr
      = __get_gh_manager__ ("opengl_renderer::draw_axes_z_grid");

    int zstate = props.get_zstate ();

    if (zstate != AXE_DEPTH_DIR && props.is_visible ()
        && (props.is_visible ()
            || (selecting && props.pickableparts_is ("all"))))
      {
        bool xySym = props.get_xySym ();
        bool zSign = props.get_zSign ();
        double zticklen = props.get_zticklen ();
        double ztickoffset = props.get_ztickoffset ();
        double fx = props.get_fx ();
        double fy = props.get_fy ();
        double xPlane = props.get_xPlane ();
        double xPlaneN = props.get_xPlaneN ();
        double yPlane = props.get_yPlane ();
        double yPlaneN = props.get_yPlaneN ();
        double z_min = props.get_z_min ();
        double z_max = props.get_z_max ();

        // Z ticks and grid properties
        Matrix zticks = xform.zscale (props.get_ztick ().matrix_value ());
        Matrix zmticks = xform.zscale (props.get_zminortickvalues ().matrix_value ());
        bool do_zminortick = props.is_zminortick () && ! zticks.isempty ();
        string_vector zticklabels = props.get_zticklabel ().string_vector_value ();
        int wmax = 0;
        int hmax = 0;
        double linewidth = props.get_linewidth ();
        std::string gridstyle = props.get_gridlinestyle ();
        std::string minorgridstyle = props.get_minorgridlinestyle ();
        Matrix gridcolor = props.get_gridcolor_rgb ();
        Matrix minorgridcolor = props.get_minorgridcolor_rgb ();
        double gridalpha = props.get_gridalpha ();
        double minorgridalpha = props.get_minorgridalpha ();
        bool do_zgrid = (props.is_zgrid () && (gridstyle != "none"));
        bool do_zminorgrid = (props.is_zminorgrid ()
                              && (minorgridstyle != "none")
                              && ! zticks.isempty ());
        bool mirror = props.is_box () && zstate != AXE_ANY_DIR;

        // Z grid

        // possibly use axis color for gridcolor & minorgridcolor
        if (props.gridcolormode_is ("auto"))
          if (props.zcolormode_is ("manual") && ! props.zcolor_is ("none"))
            gridcolor = props.get_zcolor_rgb ();

        if (props.minorgridcolormode_is ("auto"))
          if (props.zcolormode_is ("manual") && ! props.zcolor_is ("none"))
            minorgridcolor = props.get_zcolor_rgb ();

        if (gridcolor.isempty ())
          do_zgrid = false;

        if (minorgridcolor.isempty ())
          do_zminorgrid = false;

        // set styles when drawing only minor grid
        if (do_zminorgrid && ! do_zgrid)
          {
            gridstyle = minorgridstyle;
            gridcolor = minorgridcolor;
            gridalpha = minorgridalpha;
            do_zgrid = true;
          }

        // minor grid lines
        if (do_zminorgrid)
          render_grid (linewidth,
                       minorgridstyle, minorgridcolor, minorgridalpha,
                       zmticks, z_min, z_max,
                       xPlane, xPlaneN, yPlane, yPlaneN, 2, true);

        // grid lines
        if (do_zgrid)
          render_grid (linewidth,
                       gridstyle, gridcolor, gridalpha,
                       zticks, z_min, z_max,
                       xPlane, xPlaneN, yPlane, yPlaneN, 2, true);

        // Skip drawing axis, ticks, and ticklabels when color is "none"
        if (props.zcolor_is ("none"))
          return;

        set_color (props.get_zcolor_rgb ());

        // minor tick marks
        if (do_zminortick)
          {
            if (xySym)
              {
                if (math::isinf (fy))
                  render_tickmarks (zmticks, z_min, z_max, xPlaneN, xPlane,
                                    yPlane, yPlane,
                                    math::signum (xPlaneN-xPlane)*fx*zticklen/2,
                                    0., 0., 2, mirror);
                else
                  render_tickmarks (zmticks, z_min, z_max, xPlaneN, xPlaneN,
                                    yPlane, yPlane, 0.,
                                    math::signum (yPlane-yPlaneN)*fy*zticklen/2,
                                    0., 2, false);
              }
            else
              {
                if (math::isinf (fx))
                  render_tickmarks (zmticks, z_min, z_max, xPlane, xPlane,
                                    yPlaneN, yPlane, 0.,
                                    math::signum (yPlaneN-yPlane)*fy*zticklen/2,
                                    0., 2, mirror);
                else
                  render_tickmarks (zmticks, z_min, z_max, xPlane, xPlane,
                                    yPlaneN, yPlaneN,
                                    math::signum (xPlane-xPlaneN)*fx*zticklen/2,
                                    0., 0., 2, false);
              }
          }

        // tick marks
        if (xySym)
          {
            if (math::isinf (fy))
              render_tickmarks (zticks, z_min, z_max, xPlaneN, xPlane,
                                yPlane, yPlane,
                                math::signum (xPlaneN-xPlane)*fx*zticklen,
                                0., 0., 2, mirror);
            else
              render_tickmarks (zticks, z_min, z_max, xPlaneN, xPlaneN,
                                yPlane, yPlane, 0.,
                                math::signum (yPlane-yPlaneN)*fy*zticklen,
                                0., 2, false);
          }
        else
          {
            if (math::isinf (fx))
              render_tickmarks (zticks, z_min, z_max, xPlaneN, xPlane,
                                yPlaneN, yPlane, 0.,
                                math::signum (yPlaneN-yPlane)*fy*zticklen,
                                0., 2, mirror);
            else
              render_tickmarks (zticks, z_min, z_max, xPlane, xPlane,
                                yPlaneN, yPlane,
                                math::signum (xPlane-xPlaneN)*fx*zticklen,
                                0., 0., 2, false);
          }

        // tick texts
        if (zticklabels.numel () > 0)
          {
            int halign = 2;
            int valign = (zstate == AXE_VERT_DIR ? 1 : (zSign ? 3 : 2));

            if (xySym)
              {
                if (math::isinf (fy))
                  render_ticktexts (zticks, zticklabels, z_min, z_max,
                                    xPlaneN + math::signum (xPlaneN-xPlane)*fx*ztickoffset,
                                    yPlane, 2, halign, valign, wmax, hmax);
                else
                  render_ticktexts (zticks, zticklabels, z_min, z_max, xPlaneN,
                                    yPlane + math::signum (yPlane-yPlaneN)*fy*ztickoffset,
                                    2, halign, valign, wmax, hmax);
              }
            else
              {
                if (math::isinf (fx))
                  render_ticktexts (zticks, zticklabels, z_min, z_max, xPlane,
                                    yPlaneN + math::signum (yPlaneN-yPlane)*fy*ztickoffset,
                                    2, halign, valign, wmax, hmax);
                else
                  render_ticktexts (zticks, zticklabels, z_min, z_max,
                                    xPlane + math::signum (xPlane-xPlaneN)*fx*ztickoffset,
                                    yPlaneN, 2, halign, valign, wmax, hmax);
              }
          }

        gh_mgr.get_object (props.get_zlabel ()).set ("visible", "on");
      }
    else
      gh_mgr.get_object (props.get_zlabel ()).set ("visible", "off");
  }

  void
  opengl_renderer::draw_axes_grids (const axes::properties& props)
  {
#if defined (HAVE_OPENGL)
    // Disable line smoothing for axes
    GLboolean antialias;

    m_glfcns.glGetBooleanv (GL_LINE_SMOOTH, &antialias);

    if (antialias == GL_TRUE)
      m_glfcns.glDisable (GL_LINE_SMOOTH);

    set_linecap ("butt");
    set_linewidth (props.get_linewidth ());
    set_font (props);
    set_interpreter (props.get_ticklabelinterpreter ());

    draw_axes_x_grid (props);
    draw_axes_y_grid (props);
    draw_axes_z_grid (props);

    if (antialias == GL_TRUE)
      m_glfcns.glEnable (GL_LINE_SMOOTH);
#else

    octave_unused_parameter (props);

    // This shouldn't happen because construction of opengl_renderer
    // objects is supposed to be impossible if OpenGL is not available.

    panic_impossible ();

#endif
  }

  void
  opengl_renderer::draw_all_lights (const base_properties& props,
                                    std::list<graphics_object>& obj_list)
  {
#if defined (HAVE_OPENGL)
    gh_manager& gh_mgr
      = __get_gh_manager__ ("opengl_renderer::draw_axes_all_lights");

    Matrix children = props.get_all_children ();

    for (octave_idx_type i = children.numel () - 1; i >= 0; i--)
      {
        graphics_object go = gh_mgr.get_object (children(i));

        base_properties p = go.get_properties ();

        if (p.is_visible ()
            || (selecting && p.pickableparts_is ("all")))
          {
            if (go.isa ("light") && ! selecting)
              {
                if (m_current_light-GL_LIGHT0 < m_max_lights)
                  {
                    set_clipping (p.is_clipping ());
                    draw (go);
                    m_current_light++;
                  }
              }
            else if (go.isa ("hggroup")
                     && ! (selecting && p.pickableparts_is ("none")))
              draw_all_lights (go.get_properties (), obj_list);
            else if (! (selecting && p.pickableparts_is ("none")))
              obj_list.push_back (go);
          }
      }
#else

    octave_unused_parameter (props);
    octave_unused_parameter (obj_list);

    // This shouldn't happen because construction of opengl_renderer
    // objects is supposed to be impossible if OpenGL is not available.

    panic_impossible ();

#endif
  }

  void
  opengl_renderer::draw_axes_children (const axes::properties& props)
  {
#if defined (HAVE_OPENGL)
    // list for non-light child objects
    std::list<graphics_object> obj_list;
    std::list<graphics_object>::iterator it;

    // 1st pass: draw light objects

    // FIXME: max_lights only needs to be set once.
    // It would be better if this could be in the constructor for gl_renderer
    // but this seems to lead to calls of OpenGL functions before the context
    // is actually initialized.  See bug #48669.
    // Check actual maximum number of lights possible
    init_maxlights ();

    // Start with the last element of the array of child objects to
    // display them in the order they were added to the array.

    if (props.get_num_lights () > m_max_lights)
      warning_with_id ("Octave:max-lights-exceeded",
                       "light: Maximum number of lights (%d) in these axes is "
                       "exceeded.", m_max_lights);

    m_current_light = GL_LIGHT0;
    draw_all_lights (props, obj_list);

    // disable other OpenGL lights
    for (unsigned int i = props.get_num_lights (); i < m_max_lights; i++)
      m_glfcns.glDisable (GL_LIGHT0 + i);

    // save camera position and set ambient light color before drawing
    // other objects
    view_vector = props.get_cameraposition ().matrix_value ();

    float cb[4] = { 1.0, 1.0, 1.0, 1.0 };
    ColumnVector ambient_color = props.get_ambientlightcolor_rgb ();
    for (int i = 0; i < 3; i++)
      cb[i] = ambient_color(i);
    m_glfcns.glLightfv (GL_LIGHT0, GL_AMBIENT, cb);

    // 2nd pass: draw other objects (with units set to "data")

    it = obj_list.begin ();
    while (it != obj_list.end ())
      {
        graphics_object go = (*it);

        // FIXME: check whether object has "units" property and it is set
        // to "data"
        if (! go.isa ("text") || go.get ("units").string_value () == "data")
          {
            set_clipping (go.get_properties ().is_clipping ());
            draw (go);

            it = obj_list.erase (it);
          }
        else
          it++;
      }

    // 3rd pass: draw remaining objects

    m_glfcns.glDisable (GL_DEPTH_TEST);

    for (it = obj_list.begin (); it != obj_list.end (); it++)
      {
        graphics_object go = (*it);

        set_clipping (go.get_properties ().is_clipping ());
        draw (go);
      }

    set_clipping (false);

    // FIXME: finalize rendering (transparency processing)
    // FIXME: draw zoom box, if needed

#else

    octave_unused_parameter (props);

    // This shouldn't happen because construction of opengl_renderer
    // objects is supposed to be impossible if OpenGL is not available.

    panic_impossible ();

#endif
  }

  void
  opengl_renderer::draw_axes (const axes::properties& props)
  {
#if defined (HAVE_OPENGL)

    // Legends are not drawn when "visible" is "off".
    if (! props.is_visible () && props.get_tag () == "legend")
      return;

    // Don't draw the axes and its children if we are in selection and
    // pickable parts is "none".
    if (selecting && props.pickableparts_is ("none"))
      return;

    static double floatmax = std::numeric_limits<float>::max ();

    double x_min = props.get_x_min ();
    double x_max = props.get_x_max ();
    double y_min = props.get_y_min ();
    double y_max = props.get_y_max ();
    double z_min = props.get_z_min ();
    double z_max = props.get_z_max ();

    if (x_max > floatmax || y_max > floatmax || z_max > floatmax
        || x_min < -floatmax || y_min < -floatmax || z_min < -floatmax)
      {
        warning ("opengl_renderer: data values greater than float capacity.  (1) Scale data, or (2) Use gnuplot");
        return;
      }

    setup_opengl_transformation (props);

    // For 2D axes with only 2D primitives, draw from back to front without
    // depth sorting
    bool is2D = props.get_is2D (true);
    if (is2D)
      m_glfcns.glDisable (GL_DEPTH_TEST);
    else
      m_glfcns.glEnable (GL_DEPTH_TEST);

    draw_axes_planes (props);

    if (! is2D || props.layer_is ("bottom"))
      {
        draw_axes_grids (props);
        if (props.get_tag () != "legend" || props.get_box () != "off")
          draw_axes_boxes (props);
      }

    set_clipbox (x_min, x_max, y_min, y_max, z_min, z_max);

    draw_axes_children (props);

    if (is2D && props.layer_is ("top"))
      {
        draw_axes_grids (props);
        if (props.get_tag () != "legend" || props.get_box () != "off")
          draw_axes_boxes (props);
      }

#else

    octave_unused_parameter (props);

    // This shouldn't happen because construction of opengl_renderer
    // objects is supposed to be impossible if OpenGL is not available.

    panic_impossible ();

#endif
  }

  void
  opengl_renderer::draw_line (const line::properties& props)
  {
#if defined (HAVE_OPENGL)

    bool draw_all = selecting && props.pickableparts_is ("all");

    Matrix x = xform.xscale (props.get_xdata ().matrix_value ());
    Matrix y = xform.yscale (props.get_ydata ().matrix_value ());
    Matrix z = xform.zscale (props.get_zdata ().matrix_value ());

    bool has_z = (z.numel () > 0);
    int n = static_cast<int> (std::min (std::min (x.numel (), y.numel ()),
                                        (has_z ? z.numel ()
                                         : std::numeric_limits<int>::max ())));
    uint8_t clip_mask = (props.is_clipping () ? 0x7F : 0x40);
    uint8_t clip_ok = 0x40;

    std::vector<uint8_t> clip (n);

    if (has_z)
      for (int i = 0; i < n; i++)
        clip[i] = (clip_code (x(i), y(i), z(i)) & clip_mask);
    else
      {
        double z_mid = (zmin+zmax)/2;

        for (int i = 0; i < n; i++)
          clip[i] = (clip_code (x(i), y(i), z_mid) & clip_mask);
      }

    if (! props.linestyle_is ("none") && ! props.color_is ("none"))
      {
        set_color (props.get_color_rgb ());
        set_linestyle (props.get_linestyle (), false, props.get_linewidth ());
        set_linewidth (props.get_linewidth ());
        set_linecap ("butt");
        set_linejoin (props.get_linejoin ());

        if (has_z)
          {
            bool flag = false;

            for (int i = 1; i < n; i++)
              {
                if ((clip[i-1] & clip[i]) == clip_ok)
                  {
                    if (! flag)
                      {
                        flag = true;
                        m_glfcns.glBegin (GL_LINE_STRIP);
                        m_glfcns.glVertex3d (x(i-1), y(i-1), z(i-1));
                      }
                    m_glfcns.glVertex3d (x(i), y(i), z(i));
                  }
                else if (flag)
                  {
                    flag = false;
                    m_glfcns.glEnd ();
                  }
              }

            if (flag)
              m_glfcns.glEnd ();
          }
        else
          {
            bool flag = false;

            for (int i = 1; i < n; i++)
              {
                if ((clip[i-1] & clip[i]) == clip_ok)
                  {
                    if (! flag)
                      {
                        flag = true;
                        m_glfcns.glBegin (GL_LINE_STRIP);
                        m_glfcns.glVertex2d (x(i-1), y(i-1));
                      }
                    m_glfcns.glVertex2d (x(i), y(i));
                  }
                else if (flag)
                  {
                    flag = false;
                    m_glfcns.glEnd ();
                  }
              }

            if (flag)
              m_glfcns.glEnd ();
          }

        set_linewidth (0.5f);
        set_linestyle ("-");
      }

    set_clipping (false);

    if (! props.marker_is ("none")
        && ! (props.markeredgecolor_is ("none")
              && props.markerfacecolor_is ("none")))
      {
        Matrix lc, fc;

        if (draw_all)
          lc = Matrix (1, 3, 0.0);
        else if (props.markeredgecolor_is ("auto"))
          lc = props.get_color_rgb ();
        else if (! props.markeredgecolor_is ("none"))
          lc = props.get_markeredgecolor_rgb ();

        if (draw_all)
          fc = Matrix (1, 3, 0.0);
        if (props.markerfacecolor_is ("auto"))
          fc = props.get_color_rgb ();
        else if (! props.markerfacecolor_is ("none"))
          fc = props.get_markerfacecolor_rgb ();

        init_marker (props.get_marker (), props.get_markersize (),
                     props.get_linewidth ());

        for (int i = 0; i < n; i++)
          {
            if (clip[i] == clip_ok)
              draw_marker (x(i), y(i),
                           has_z ? z(i) : 0.0,
                           lc, fc);
          }

        end_marker ();
      }

    set_clipping (props.is_clipping ());

#else

    octave_unused_parameter (props);

    // This shouldn't happen because construction of opengl_renderer
    // objects is supposed to be impossible if OpenGL is not available.

    panic_impossible ();

#endif
  }

  void
  opengl_renderer::draw_surface (const surface::properties& props)
  {
#if defined (HAVE_OPENGL)

    bool draw_all = selecting && props.pickableparts_is ("all");

    const Matrix x = xform.xscale (props.get_xdata ().matrix_value ());
    const Matrix y = xform.yscale (props.get_ydata ().matrix_value ());
    const Matrix z = xform.zscale (props.get_zdata ().matrix_value ());

    int zr = z.rows ();
    int zc = z.columns ();

    NDArray c;
    const NDArray vn = props.get_vertexnormals ().array_value ();
    dim_vector vn_dims = vn.dims ();
    bool has_vertex_normals = (vn_dims(0) == zr && vn_dims(1) == zc
                               && vn_dims(2) == 3);
    const NDArray fn = props.get_facenormals ().array_value ();
    dim_vector fn_dims = fn.dims ();
    bool has_face_normals = (fn_dims(0) == zr - 1 && fn_dims(1) == zc - 1
                             && fn_dims(2) == 3);

    // FIXME: handle transparency
    Matrix a;

    int fc_mode = (props.facecolor_is_rgb () ? 0 :
                   (props.facecolor_is ("flat") ? 1 :
                    (props.facecolor_is ("interp") ? 2 :
                     (props.facecolor_is ("texturemap") ? 3 : -1))));
    int fl_mode = (props.facelighting_is ("none") ? 0 :
                   (props.facelighting_is ("flat") ?
                    (has_face_normals ? 1 : 0) :
                    (has_vertex_normals ? 2 : 0)));
    int fa_mode = (props.facealpha_is_double () ? 0 :
                   (props.facealpha_is ("flat") ? 1 : 2));
    int ec_mode = (props.edgecolor_is_rgb () ? 0 :
                   (props.edgecolor_is ("flat") ? 1 :
                    (props.edgecolor_is ("interp") ? 2 : -1)));
    int el_mode = (props.edgelighting_is ("none") ? 0 :
                   (props.edgelighting_is ("flat") ?
                    (has_face_normals ? 1 : 0) :
                    (has_vertex_normals ? 2 : 0)));
    int ea_mode = (props.edgealpha_is_double () ? 0 :
                   (props.edgealpha_is ("flat") ? 1 : 2));
    int bfl_mode = (props.backfacelighting_is ("lit") ? 0 :
                    (props.backfacelighting_is ("reverselit") ? 1 : 2));
    bool do_lighting = props.get_do_lighting ();

    Matrix fcolor = (fc_mode == TEXTURE ? Matrix (1, 3, 1.0)
                                        : props.get_facecolor_rgb ());
    Matrix ecolor = props.get_edgecolor_rgb ();
    double fa = 1.0;

    float as = props.get_ambientstrength ();
    float ds = props.get_diffusestrength ();
    float ss = props.get_specularstrength ();
    float se = props.get_specularexponent () * 5; // to fit Matlab
    float scr = props.get_specularcolorreflectance ();
    float cb[4] = { 0.0, 0.0, 0.0, 1.0 };

    opengl_texture tex (m_glfcns);

    int i1, i2, j1, j2;
    bool x_mat = (x.rows () == z.rows ());
    bool y_mat = (y.columns () == z.columns ());

    i1 = i2 = j1 = j2 = 0;

    if ((fc_mode > 0 && fc_mode < 3) || ec_mode > 0)
      c = props.get_color_data ().array_value ();

    boolMatrix clip (z.dims (), false);

    for (int i = 0; i < zr; i++)
      {
        if (x_mat)
          i1 = i;

        for (int j = 0; j < zc; j++)
          {
            if (y_mat)
              j1 = j;

            clip(i,j) = is_nan_or_inf (x(i1,j), y(i,j1), z(i,j));
          }
      }

    if (fa_mode > 0 || ea_mode > 0)
      {
        // FIXME: implement alphadata conversion
        //a = props.get_alpha_data ();
      }

    if (fl_mode > 0 || el_mode > 0)
      m_glfcns.glMaterialf (LIGHT_MODE, GL_SHININESS, se);

    // FIXME: good candidate for caching,
    //        transferring pixel data to OpenGL is time consuming.
    if (fc_mode == TEXTURE)
      tex = opengl_texture::create (m_glfcns, props.get_color_data ());

    if (draw_all || ! props.facecolor_is ("none"))
      {
        if (fa_mode == 0)
          {
            fa = props.get_facealpha_double ();
            cb[3] = fa;
            if (fc_mode == UNIFORM || fc_mode == TEXTURE)
              {
                m_glfcns.glColor4d (fcolor(0), fcolor(1), fcolor(2), fa);
                if (fl_mode > 0)
                  {
                    for (int i = 0; i < 3; i++)
                      cb[i] = as * fcolor(i);
                    m_glfcns.glMaterialfv (LIGHT_MODE, GL_AMBIENT, cb);

                    for (int i = 0; i < 3; i++)
                      cb[i] = ds * fcolor(i);
                    m_glfcns.glMaterialfv (LIGHT_MODE, GL_DIFFUSE, cb);

                    for (int i = 0; i < 3; i++)
                      cb[i] = ss * (scr + (1-scr) * fcolor(i));
                    m_glfcns.glMaterialfv (LIGHT_MODE, GL_SPECULAR, cb);
                  }
              }

            if ((fl_mode > 0) && do_lighting)
              m_glfcns.glEnable (GL_LIGHTING);
            m_glfcns.glShadeModel ((fc_mode == INTERP || fl_mode == GOURAUD)
                                   ? GL_SMOOTH : GL_FLAT);
            set_polygon_offset (true, 1.0);
            if (fc_mode == TEXTURE)
              m_glfcns.glEnable (GL_TEXTURE_2D);

            for (int i = 1; i < zc; i++)
              {
                if (y_mat)
                  {
                    i1 = i-1;
                    i2 = i;
                  }

                for (int j = 1; j < zr; j++)
                  {

                    if (clip(j-1, i-1) || clip(j, i-1)
                        || clip(j-1, i) || clip(j, i))
                      continue;

                    if (fc_mode == FLAT)
                      {
                        // "flat" only needs color at lower-left vertex
                        if (! math::isfinite (c(j-1,i-1)))
                          continue;
                      }
                    else if (fc_mode == INTERP)
                      {
                        // "interp" needs valid color at all 4 vertices
                        if (! (math::isfinite (c(j-1, i-1)) && math::isfinite (c(j, i-1))
                               && math::isfinite (c(j-1, i)) && math::isfinite (c(j, i))))
                          continue;
                      }

                    if (x_mat)
                      {
                        j1 = j-1;
                        j2 = j;
                      }

                    m_glfcns.glBegin (GL_QUADS);

                    // Vertex 1
                    if (fc_mode == TEXTURE)
                      tex.tex_coord (double (i-1) / (zc-1),
                                     double (j-1) / (zr-1));
                    else if (fc_mode > 0)
                      {
                        // FIXME: is there a smarter way to do this?
                        for (int k = 0; k < 3; k++)
                          cb[k] = c(j-1, i-1, k);
                        m_glfcns.glColor4fv (cb);

                        if (fl_mode > 0)
                          {
                            for (int k = 0; k < 3; k++)
                              cb[k] *= as;
                            m_glfcns.glMaterialfv (LIGHT_MODE, GL_AMBIENT, cb);

                            for (int k = 0; k < 3; k++)
                              cb[k] = ds * c(j-1, i-1, k);
                            m_glfcns.glMaterialfv (LIGHT_MODE, GL_DIFFUSE, cb);

                            for (int k = 0; k < 3; k++)
                              cb[k] = ss * (scr + (1-scr) * c(j-1, i-1, k));
                            m_glfcns.glMaterialfv (LIGHT_MODE, GL_SPECULAR, cb);
                          }
                      }
                    if (fl_mode > 0)
                      set_normal (bfl_mode, (fl_mode == GOURAUD ? vn : fn),
                                  j-1, i-1);

                    m_glfcns.glVertex3d (x(j1,i-1), y(j-1,i1), z(j-1,i-1));

                    // Vertex 2
                    if (fc_mode == TEXTURE)
                      tex.tex_coord (double (i) / (zc-1), double (j-1) / (zr-1));
                    else if (fc_mode == INTERP)
                      {
                        for (int k = 0; k < 3; k++)
                          cb[k] = c(j-1, i, k);
                        m_glfcns.glColor4fv (cb);

                        if (fl_mode > 0)
                          {
                            for (int k = 0; k < 3; k++)
                              cb[k] *= as;
                            m_glfcns.glMaterialfv (LIGHT_MODE, GL_AMBIENT, cb);

                            for (int k = 0; k < 3; k++)
                              cb[k] = ds * c(j-1, i, k);
                            m_glfcns.glMaterialfv (LIGHT_MODE, GL_DIFFUSE, cb);

                            for (int k = 0; k < 3; k++)
                              cb[k] = ss * (scr + (1-scr) * c(j-1, i, k));
                            m_glfcns.glMaterialfv (LIGHT_MODE, GL_SPECULAR, cb);
                          }
                      }

                    if (fl_mode == GOURAUD)
                      set_normal (bfl_mode, vn, j-1, i);

                    m_glfcns.glVertex3d (x(j1,i), y(j-1,i2), z(j-1,i));

                    // Vertex 3
                    if (fc_mode == TEXTURE)
                      tex.tex_coord (double (i) / (zc-1), double (j) / (zr-1));
                    else if (fc_mode == INTERP)
                      {
                        for (int k = 0; k < 3; k++)
                          cb[k] = c(j, i, k);
                        m_glfcns.glColor4fv (cb);

                        if (fl_mode > 0)
                          {
                            for (int k = 0; k < 3; k++)
                              cb[k] *= as;
                            m_glfcns.glMaterialfv (LIGHT_MODE, GL_AMBIENT, cb);

                            for (int k = 0; k < 3; k++)
                              cb[k] = ds * c(j, i, k);
                            m_glfcns.glMaterialfv (LIGHT_MODE, GL_DIFFUSE, cb);

                            for (int k = 0; k < 3; k++)
                              cb[k] = ss * (scr + (1-scr) * c(j, i, k));
                            m_glfcns.glMaterialfv (LIGHT_MODE, GL_SPECULAR, cb);
                          }
                      }
                    if (fl_mode == GOURAUD)
                      set_normal (bfl_mode, vn, j, i);

                    m_glfcns.glVertex3d (x(j2,i), y(j,i2), z(j,i));

                    // Vertex 4
                    if (fc_mode == TEXTURE)
                      tex.tex_coord (double (i-1) / (zc-1), double (j) / (zr-1));
                    else if (fc_mode == INTERP)
                      {
                        for (int k = 0; k < 3; k++)
                          cb[k] = c(j, i-1, k);
                        m_glfcns.glColor4fv (cb);

                        if (fl_mode > 0)
                          {
                            for (int k = 0; k < 3; k++)
                              cb[k] *= as;
                            m_glfcns.glMaterialfv (LIGHT_MODE, GL_AMBIENT, cb);

                            for (int k = 0; k < 3; k++)
                              cb[k] = ds * c(j, i-1, k);
                            m_glfcns.glMaterialfv (LIGHT_MODE, GL_DIFFUSE, cb);

                            for (int k = 0; k < 3; k++)
                              cb[k] = ss * (scr + (1-scr) * c(j, i-1, k));
                            m_glfcns.glMaterialfv (LIGHT_MODE, GL_SPECULAR, cb);
                          }
                      }
                    if (fl_mode == GOURAUD)
                      set_normal (bfl_mode, vn, j, i-1);

                    m_glfcns.glVertex3d (x(j2,i-1), y(j,i1), z(j,i-1));

                    m_glfcns.glEnd ();
                  }
              }

            set_polygon_offset (false);
            if (fc_mode == TEXTURE)
              m_glfcns.glDisable (GL_TEXTURE_2D);

            if ((fl_mode > 0) && do_lighting)
              m_glfcns.glDisable (GL_LIGHTING);
          }
        else
          {
            // FIXME: implement flat, interp and texturemap transparency
          }
      }

    if (! props.edgecolor_is ("none") && ! props.linestyle_is ("none"))
      {
        if (props.get_edgealpha_double () == 1)
          {
            cb[3] = 1.0; // edgealpha isn't implemented yet
            if (ec_mode == UNIFORM)
              {
                m_glfcns.glColor3dv (ecolor.data ());
                if (el_mode > 0)
                  {
                    for (int i = 0; i < 3; i++)
                      cb[i] = as * ecolor(i);
                    m_glfcns.glMaterialfv (LIGHT_MODE, GL_AMBIENT, cb);

                    for (int i = 0; i < 3; i++)
                      cb[i] = ds * ecolor(i);
                    m_glfcns.glMaterialfv (LIGHT_MODE, GL_DIFFUSE, cb);

                    for (int i = 0; i < 3; i++)
                      cb[i] = ss * (scr + (1-scr) * ecolor(i));
                    m_glfcns.glMaterialfv (LIGHT_MODE, GL_SPECULAR, cb);
                  }
              }

            if ((el_mode > 0) && do_lighting)
              m_glfcns.glEnable (GL_LIGHTING);
            m_glfcns.glShadeModel ((ec_mode == INTERP || el_mode == GOURAUD)
                                   ? GL_SMOOTH : GL_FLAT);

            set_linestyle (props.get_linestyle (), false,
                           props.get_linewidth ());
            set_linewidth (props.get_linewidth ());
            set_linecap ("butt");
            set_linejoin ("miter");

            // Mesh along Y-axis

            if (props.meshstyle_is ("both") || props.meshstyle_is ("column"))
              {
                for (int i = 0; i < zc; i++)
                  {
                    if (y_mat)
                      {
                        i1 = i-1;
                        i2 = i;
                      }

                    for (int j = 1; j < zr; j++)
                      {
                        if (clip(j-1,i) || clip(j,i))
                          continue;

                        if (ec_mode == FLAT)
                          {
                            // "flat" only needs color at lower-left vertex
                            if (! math::isfinite (c(j-1,i)))
                              continue;
                          }
                        else if (ec_mode == INTERP)
                          {
                            // "interp" needs valid color at both vertices
                            if (! (math::isfinite (c(j-1, i)) && math::isfinite (c(j, i))))
                              continue;
                          }

                        if (x_mat)
                          {
                            j1 = j-1;
                            j2 = j;
                          }

                        m_glfcns.glBegin (GL_LINES);

                        // Vertex 1
                        if (ec_mode > 0)
                          {
                            for (int k = 0; k < 3; k++)
                              cb[k] = c(j-1, i, k);
                            m_glfcns.glColor3fv (cb);

                            if (el_mode > 0)
                              {
                                for (int k = 0; k < 3; k++)
                                  cb[k] *= as;
                                m_glfcns.glMaterialfv (LIGHT_MODE, GL_AMBIENT, cb);

                                for (int k = 0; k < 3; k++)
                                  cb[k] = ds * c(j-1, i, k);
                                m_glfcns.glMaterialfv (LIGHT_MODE, GL_DIFFUSE, cb);

                                for (int k = 0; k < 3; k++)
                                  cb[k] = ss * (scr + (1-scr) * c(j-1, i, k));
                                m_glfcns.glMaterialfv (LIGHT_MODE, GL_SPECULAR, cb);
                              }
                          }
                        if (el_mode > 0)
                          {
                            if (el_mode == GOURAUD)
                              set_normal (bfl_mode, vn, j-1, i);
                            else
                              set_normal (bfl_mode, fn, j-1, std::min (i, zc-2));
                          }

                        m_glfcns.glVertex3d (x(j1,i), y(j-1,i2), z(j-1,i));

                        // Vertex 2
                        if (ec_mode == INTERP)
                          {
                            for (int k = 0; k < 3; k++)
                              cb[k] = c(j, i, k);
                            m_glfcns.glColor3fv (cb);

                            if (el_mode > 0)
                              {
                                for (int k = 0; k < 3; k++)
                                  cb[k] *= as;
                                m_glfcns.glMaterialfv (LIGHT_MODE, GL_AMBIENT, cb);

                                for (int k = 0; k < 3; k++)
                                  cb[k] = ds * c(j, i, k);
                                m_glfcns.glMaterialfv (LIGHT_MODE, GL_DIFFUSE, cb);

                                for (int k = 0; k < 3; k++)
                                  cb[k] = ss * (scr + (1-scr) * c(j, i, k));
                                m_glfcns.glMaterialfv (LIGHT_MODE, GL_SPECULAR, cb);
                              }
                          }
                        if (el_mode == GOURAUD)
                          set_normal (bfl_mode, vn, j, i);

                        m_glfcns.glVertex3d (x(j2,i), y(j,i2), z(j,i));

                        m_glfcns.glEnd ();
                      }
                  }
              }

            // Mesh along X-axis

            if (props.meshstyle_is ("both") || props.meshstyle_is ("row"))
              {
                for (int j = 0; j < zr; j++)
                  {
                    if (x_mat)
                      {
                        j1 = j-1;
                        j2 = j;
                      }

                    for (int i = 1; i < zc; i++)
                      {
                        if (clip(j,i-1) || clip(j,i))
                          continue;

                        if (ec_mode == FLAT)
                          {
                            // "flat" only needs color at lower-left vertex
                            if (! math::isfinite (c(j,i-1)))
                              continue;
                          }
                        else if (ec_mode == INTERP)
                          {
                            // "interp" needs valid color at both vertices
                            if (! (math::isfinite (c(j, i-1)) && math::isfinite (c(j, i))))
                              continue;
                          }

                        if (y_mat)
                          {
                            i1 = i-1;
                            i2 = i;
                          }

                        m_glfcns.glBegin (GL_LINES);

                        // Vertex 1
                        if (ec_mode > 0)
                          {
                            for (int k = 0; k < 3; k++)
                              cb[k] = c(j, i-1, k);
                            m_glfcns.glColor3fv (cb);

                            if (el_mode > 0)
                              {
                                for (int k = 0; k < 3; k++)
                                  cb[k] *= as;
                                m_glfcns.glMaterialfv (LIGHT_MODE, GL_AMBIENT, cb);

                                for (int k = 0; k < 3; k++)
                                  cb[k] = ds * c(j, i-1, k);
                                m_glfcns.glMaterialfv (LIGHT_MODE, GL_DIFFUSE, cb);

                                for (int k = 0; k < 3; k++)
                                  cb[k] = ss * (scr + (1-scr) * c(j, i-1, k));
                                m_glfcns.glMaterialfv (LIGHT_MODE, GL_SPECULAR, cb);
                              }
                          }
                        if (el_mode > 0)
                          {
                            if (el_mode == GOURAUD)
                              set_normal (bfl_mode, vn, j, i-1);
                            else
                              set_normal (bfl_mode, fn, std::min (j, zr-2), i-1);
                          }

                        m_glfcns.glVertex3d (x(j2,i-1), y(j,i1), z(j,i-1));

                        // Vertex 2
                        if (ec_mode == INTERP)
                          {
                            for (int k = 0; k < 3; k++)
                              cb[k] = c(j, i, k);
                            m_glfcns.glColor3fv (cb);

                            if (el_mode > 0)
                              {
                                for (int k = 0; k < 3; k++)
                                  cb[k] *= as;
                                m_glfcns.glMaterialfv (LIGHT_MODE, GL_AMBIENT, cb);

                                for (int k = 0; k < 3; k++)
                                  cb[k] = ds * c(j, i, k);
                                m_glfcns.glMaterialfv (LIGHT_MODE, GL_DIFFUSE, cb);

                                for (int k = 0; k < 3; k++)
                                  cb[k] = ss * (scr + (1-scr) * c(j, i, k));
                                m_glfcns.glMaterialfv (LIGHT_MODE, GL_SPECULAR, cb);
                              }
                          }
                        if (el_mode == GOURAUD)
                          set_normal (bfl_mode, vn, j, i);

                        m_glfcns.glVertex3d (x(j2,i), y(j,i2), z(j,i));

                        m_glfcns.glEnd ();
                      }
                  }
              }

            set_linestyle ("-");  // Disable LineStipple
            set_linewidth (0.5f);

            if ((el_mode > 0) && do_lighting)
              m_glfcns.glDisable (GL_LIGHTING);
          }
        else
          {
            // FIXME: implement transparency
          }
      }

    if (! props.marker_is ("none")
        && ! (props.markeredgecolor_is ("none")
              && props.markerfacecolor_is ("none")))
      {
        // FIXME: check how transparency should be handled in markers
        // FIXME: check what to do with marker facecolor set to auto
        //        and facecolor set to none.

        bool do_edge = draw_all || ! props.markeredgecolor_is ("none");
        bool do_face = draw_all || ! props.markerfacecolor_is ("none");

        Matrix mecolor = (draw_all ? Matrix (1, 3, 0.0) :
                          props.get_markeredgecolor_rgb ());
        Matrix mfcolor = (draw_all ? Matrix (1, 3, 0.0) :
                          props.get_markerfacecolor_rgb ());
        Matrix cc (1, 3, 0.0);

        if (mecolor.isempty () && props.markeredgecolor_is ("auto"))
          {
            mecolor = props.get_edgecolor_rgb ();
            do_edge = ! props.edgecolor_is ("none");
          }

        if (mfcolor.isempty () && props.markerfacecolor_is ("auto"))
          {
            mfcolor = props.get_facecolor_rgb ();
            do_face = ! props.facecolor_is ("none");
          }

        if ((mecolor.isempty () || mfcolor.isempty ()) && c.isempty ())
          c = props.get_color_data ().array_value ();

        init_marker (props.get_marker (), props.get_markersize (),
                     props.get_linewidth ());

        uint8_t clip_mask = (props.is_clipping () ? 0x7F : 0x40);
        uint8_t clip_ok = 0x40;

        for (int i = 0; i < zc; i++)
          {
            if (y_mat)
              i1 = i;

            for (int j = 0; j < zr; j++)
              {
                if (x_mat)
                  j1 = j;

                if ((clip_code (x(j1,i), y(j,i1), z(j,i)) & clip_mask)
                    != clip_ok)
                  continue;

                if ((do_edge && mecolor.isempty ())
                    || (do_face && mfcolor.isempty ()))
                  {
                    if (! math::isfinite (c(j,i)))
                      continue;  // Skip NaNs in color data

                    for (int k = 0; k < 3; k++)
                      cc(k) = c(j,i,k);
                  }

                Matrix lc = (do_edge ? (mecolor.isempty () ? cc : mecolor)
                                     : Matrix ());
                Matrix fc = (do_face ? (mfcolor.isempty () ? cc : mfcolor)
                                     : Matrix ());

                draw_marker (x(j1,i), y(j,i1), z(j,i), lc, fc);
              }
          }

        end_marker ();
      }

#else

    octave_unused_parameter (props);

    // This shouldn't happen because construction of opengl_renderer
    // objects is supposed to be impossible if OpenGL is not available.

    panic_impossible ();

#endif
  }

  // FIXME: global optimization (rendering, data structures...),
  // there is probably a smarter/faster/less-memory-consuming way to do this.
  void
  opengl_renderer::draw_patch (const patch::properties& props)
  {
#if defined (HAVE_OPENGL)

    // Do not render if the patch has incoherent data
    std::string msg;
    if (props.has_bad_data (msg))
      {
        warning ("opengl_renderer: %s.  Not rendering.", msg.c_str ());
        return;
      }

    bool draw_all = selecting && props.pickableparts_is ("all");
    const Matrix f = props.get_faces ().matrix_value ();
    const Matrix v = xform.scale (props.get_vertices ().matrix_value ());
    Matrix c;
    Matrix a;
    double fa = 1.0;

    int nv = v.rows ();
    int nf = f.rows ();
    int fcmax = f.columns ();

    bool has_z = (v.columns () > 2);
    bool has_facecolor = false;
    bool has_facealpha = false;

    int fc_mode = ((props.facecolor_is ("none")
                    || props.facecolor_is_rgb () || draw_all) ? 0 :
                   (props.facecolor_is ("flat") ? 1 : 2));
    int fl_mode = (props.facelighting_is ("none") ? 0 :
                   (props.facelighting_is ("flat") ? 1 : 2));
    int fa_mode = (props.facealpha_is_double () ? 0 :
                   (props.facealpha_is ("flat") ? 1 : 2));
    int ec_mode = ((props.edgecolor_is ("none")
                    || props.edgecolor_is_rgb ()) ? 0 :
                   (props.edgecolor_is ("flat") ? 1 : 2));
    int el_mode = (props.edgelighting_is ("none") ? 0 :
                   (props.edgelighting_is ("flat") ? 1 : 2));
    int ea_mode = (props.edgealpha_is_double () ? 0 :
                   (props.edgealpha_is ("flat") ? 1 : 2));
    int bfl_mode = (props.backfacelighting_is ("lit") ? 0 :
                    (props.backfacelighting_is ("reverselit") ? 1 : 2));
    bool do_lighting = props.get_do_lighting ();

    Matrix fcolor = props.get_facecolor_rgb ();
    Matrix ecolor = props.get_edgecolor_rgb ();

    float as = props.get_ambientstrength ();
    float ds = props.get_diffusestrength ();
    float ss = props.get_specularstrength ();
    float se = props.get_specularexponent () * 5; // to fit Matlab
    float scr = props.get_specularcolorreflectance ();

    const Matrix vn = props.get_vertexnormals ().matrix_value ();
    bool has_vertex_normals = (vn.rows () == nv);
    const Matrix fn = props.get_facenormals ().matrix_value ();
    bool has_face_normals = (fn.rows () == nf);

    boolMatrix clip (1, nv, false);

    if (has_z)
      for (int i = 0; i < nv; i++)
        clip(i) = is_nan_or_inf (v(i,0), v(i,1), v(i,2));
    else
      for (int i = 0; i < nv; i++)
        clip(i) = is_nan_or_inf (v(i,0), v(i,1), 0);

    boolMatrix clip_f (1, nf, false);
    Array<int> count_f (dim_vector (nf, 1), 0);

    for (int i = 0; i < nf; i++)
      {
        bool fclip = false;
        int count = 0;

        for (int j = 0; j < fcmax && ! math::isnan (f(i,j)); j++, count++)
          fclip = (fclip || clip(int (f(i,j) - 1)));

        clip_f(i) = fclip;
        count_f(i) = count;
      }

    if (draw_all || fc_mode > 0 || ec_mode > 0)
      {
        if (draw_all)
          c = Matrix (1, 3, 0.0);
        else
          c = props.get_color_data ().matrix_value ();

        if (c.rows () == 1)
          {
            // Single color specifications, we can simplify a little bit

            if (draw_all || fc_mode > 0)
              {
                fcolor = c;
                fc_mode = UNIFORM;
              }

            if (draw_all || ec_mode > 0)
              {
                ecolor = c;
                ec_mode = UNIFORM;
              }

            c = Matrix ();
          }
        else
          has_facecolor = ((c.numel () > 0) && (c.rows () == f.rows ()));
      }

    if (fa_mode > 0 || ea_mode > 0)
      {
        // FIXME: retrieve alpha data from patch object
        //a = props.get_alpha_data ();
        has_facealpha = ((a.numel () > 0) && (a.rows () == f.rows ()));
      }

    if (fa_mode == 0)
      fa = props.get_facealpha_double ();

    octave_idx_type fr = f.rows ();
    std::vector<vertex_data> vdata (f.numel ());

    for (int i = 0; i < nf; i++)
      for (int j = 0; j < count_f(i); j++)
        {
          int idx = int (f(i,j) - 1);

          Matrix vv (1, 3, 0.0);
          Matrix cc;
          Matrix vnn (1, 3, 0.0);
          Matrix fnn (1, 3, 0.0);
          double aa = 1.0;

          vv(0) = v(idx,0); vv(1) = v(idx,1);
          if (has_z)
            vv(2) = v(idx,2);
          if (((fl_mode == FLAT) || (el_mode == FLAT)) && has_face_normals)
            {
              double dir = 1.0;
              if (bfl_mode > 0)
                dir = ((fn(i,0) * view_vector(0)
                        + fn(i,1) * view_vector(1)
                        + fn(i,2) * view_vector(2) < 0)
                       ? ((bfl_mode > 1) ? 0.0 : -1.0) : 1.0);
              fnn(0) = dir * fn(i,0);
              fnn(1) = dir * fn(i,1);
              fnn(2) = dir * fn(i,2);
            }
          if ((fl_mode == GOURAUD || el_mode == GOURAUD) && has_vertex_normals)
            {
              double dir = 1.0;
              if (bfl_mode > 0)
                dir = ((vn(idx,0) * view_vector(0)
                        + vn(idx,1) * view_vector(1)
                        + vn(idx,2) * view_vector(2) < 0)
                       ? ((bfl_mode > 1) ? 0.0 : -1.0) : 1.0);
              vnn(0) = dir * vn(idx,0);
              vnn(1) = dir * vn(idx,1);
              vnn(2) = dir * vn(idx,2);
            }
          if (c.numel () > 0)
            {
              cc.resize (1, 3);
              if (has_facecolor)
                cc(0) = c(i,0), cc(1) = c(i,1), cc(2) = c(i,2);
              else
                cc(0) = c(idx,0), cc(1) = c(idx,1), cc(2) = c(idx,2);
            }
          if (fa_mode == 0)
            aa = fa;
          else if (a.numel () > 0)
            {
              if (has_facealpha)
                aa = a(i);
              else
                aa = a(idx);
            }

          vdata[i+j*fr] = vertex_data (vv, cc, vnn, fnn, aa, as, ds, ss, se, scr);
        }

    if (fl_mode > 0 || el_mode > 0)
      m_glfcns.glMaterialf (LIGHT_MODE, GL_SHININESS, se);

    if (draw_all || ! props.facecolor_is ("none"))
      {
        // FIXME: adapt to double-radio property
        if (fa_mode == 0)
          {
            if (fc_mode == UNIFORM)
              {
                m_glfcns.glColor4d (fcolor(0), fcolor(1), fcolor(2), fa);
                if (fl_mode > 0)
                  {
                    float cb[4] = { 0.0f, 0.0f, 0.0f, 1.0f };;

                    for (int i = 0; i < 3; i++)
                      cb[i] = as * fcolor(i);
                    m_glfcns.glMaterialfv (LIGHT_MODE, GL_AMBIENT, cb);

                    for (int i = 0; i < 3; i++)
                      cb[i] = ds * fcolor(i);
                    m_glfcns.glMaterialfv (LIGHT_MODE, GL_DIFFUSE, cb);

                    for (int i = 0; i < 3; i++)
                      cb[i] = ss * (scr + (1-scr) * fcolor(i));
                    m_glfcns.glMaterialfv (LIGHT_MODE, GL_SPECULAR, cb);
                  }
              }

            if ((fl_mode > 0) && do_lighting)
              m_glfcns.glEnable (GL_LIGHTING);

            // NOTE: Push filled part of patch backwards to avoid Z-fighting
            // with tessellator outline.  A value of 1.0 seems to work fine.
            // Value can't be too large or the patch will be pushed below the
            // axes planes at +2.5.
            patch_tessellator tess (this, fc_mode, fl_mode, true, 1.0);

            std::vector<octave_idx_type>::const_iterator it;
            octave_idx_type i_start, i_end;

            for (int i = 0; i < nf; i++)
              {
                if (clip_f(i))
                  continue;

                bool is_non_planar = false;
                if (props.coplanar_last_idx.size () > 0
                    && props.coplanar_last_idx[i].size () > 1)
                  {
                    is_non_planar = true;
                    it = props.coplanar_last_idx[i].end ();
                    it--;
                  }

                // loop over planar subsets of face
                do
                  {
                    if (is_non_planar)
                      {
                        i_end = *it;
                        if (it == props.coplanar_last_idx[i].begin ())
                          i_start = 0;
                        else
                          {
                            it--;
                            i_start = *it - 1;
                          }
                      }
                    else
                      {
                        i_end = count_f(i) - 1;
                        i_start = 0;
                      }

                    tess.begin_polygon (true);
                    tess.begin_contour ();

                    // Add vertices in reverse order for Matlab compatibility
                    for (int j = i_end; j > i_start; j--)
                      {
                        vertex_data::vertex_data_rep *vv
                          = vdata[i+j*fr].get_rep ();

                        tess.add_vertex (vv->coords.fortran_vec (), vv);
                      }

                    if (count_f(i) > 0)
                      {
                        vertex_data::vertex_data_rep *vv = vdata[i].get_rep ();

                        if (fc_mode == FLAT)
                          {
                            // For "flat" shading, use color of 1st vertex.
                            Matrix col = vv->color;

                            if (col.numel () == 3)
                              {
                                m_glfcns.glColor4d (col(0), col(1), col(2), fa);
                                if (fl_mode > 0)
                                  {
                                    float cb[4] = { 0.0f, 0.0f, 0.0f, 1.0f };

                                    for (int k = 0; k < 3; k++)
                                      cb[k] = (vv->ambient * col(k));
                                    m_glfcns.glMaterialfv (LIGHT_MODE, GL_AMBIENT, cb);

                                    for (int k = 0; k < 3; k++)
                                      cb[k] = (vv->diffuse * col(k));
                                    m_glfcns.glMaterialfv (LIGHT_MODE, GL_DIFFUSE, cb);

                                    for (int k = 0; k < 3; k++)
                                      cb[k] = vv->specular *
                                              (vv->specular_color_refl
                                               + (1-vv->specular_color_refl) *
                                              col(k));
                                    m_glfcns.glMaterialfv (LIGHT_MODE, GL_SPECULAR, cb);
                                  }
                              }
                          }

                        tess.add_vertex (vv->coords.fortran_vec (), vv);
                      }

                    tess.end_contour ();
                    tess.end_polygon ();
                  } while (i_start > 0);
              }

            if ((fl_mode > 0) && do_lighting)
              m_glfcns.glDisable (GL_LIGHTING);
          }
        else
          {
            // FIXME: implement flat and interp transparency
          }
      }

    if (draw_all
        || (! props.edgecolor_is ("none") && ! props.linestyle_is ("none")))
      {
        // FIXME: adapt to double-radio property
        if (props.get_edgealpha_double () == 1)
          {
            if (ec_mode == UNIFORM)
              {
                m_glfcns.glColor3dv (ecolor.data ());
                if (el_mode > 0)
                  {
                    // edge lighting only uses ambient light
                    float cb[4] = { 0.0f, 0.0f, 0.0f, 1.0f };
                    m_glfcns.glMaterialfv (LIGHT_MODE, GL_SPECULAR, cb);
                    m_glfcns.glMaterialfv (LIGHT_MODE, GL_DIFFUSE, cb);

                    for (int i = 0; i < 3; i++)
                      cb[i] = (as * ecolor(i));
                    m_glfcns.glMaterialfv (LIGHT_MODE, GL_AMBIENT, cb);
                  }
              }

            if ((el_mode > 0) && do_lighting)
              m_glfcns.glEnable (GL_LIGHTING);

            double linewidth = props.get_linewidth ();
            set_linestyle (props.get_linestyle (), false, linewidth);
            set_linewidth (linewidth);
            set_linecap ("butt");
            set_linejoin ("miter");

            // NOTE: patch contour cannot be offset.  Offset must occur with the
            // filled portion of the patch above.  The tessellator uses
            // GLU_TESS_BOUNDARY_ONLY to get the outline of the patch and OpenGL
            // automatically sets the glType to GL_LINE_LOOP.  This primitive is
            // not supported by glPolygonOffset which is used to do Z offsets.
            patch_tessellator tess (this, ec_mode, el_mode, false);

            for (int i = 0; i < nf; i++)
              {
                bool is_non_planar = false;
                if (props.coplanar_last_idx.size () > 0
                    && props.coplanar_last_idx[i].size () > 1)
                  is_non_planar = true;
                if (clip_f(i) || is_non_planar)
                  {
                    // This is an unclosed contour or a non-planar face.
                    // Draw it as a line.
                    bool flag = false;

                    m_glfcns.glShadeModel ((ec_mode == INTERP || el_mode == GOURAUD)
                                           ? GL_SMOOTH : GL_FLAT);

                    // Add vertices in reverse order for Matlab compatibility
                    for (int j = count_f(i)-1; j >= 0; j--)
                      {
                        if (! clip(int (f(i,j) - 1)))
                          {
                            vertex_data::vertex_data_rep *vv
                              = vdata[i+j*fr].get_rep ();
                            const Matrix m = vv->coords;
                            if (! flag)
                              {
                                flag = true;
                                m_glfcns.glBegin (GL_LINE_STRIP);
                              }
                            if (ec_mode != UNIFORM)
                              {
                                Matrix col = vv->color;

                                if (col.numel () == 3)
                                  m_glfcns.glColor3dv (col.data ());
                              }
                            m_glfcns.glVertex3d (m(0), m(1), m(2));
                          }
                        else if (flag)
                          {
                            flag = false;
                            m_glfcns.glEnd ();
                          }
                      }
                    // Do loop body with vertex N to "close" GL_LINE_STRIP
                    // from vertex 0 to vertex N.
                    int j = count_f(i)-1;
                    if (flag && ! clip(int (f(i,j) - 1)))
                      {
                        vertex_data::vertex_data_rep *vv
                          = vdata[i+j*fr].get_rep ();
                        const Matrix m = vv->coords;
                        if (ec_mode != UNIFORM)
                          {
                            Matrix col = vv->color;

                            if (col.numel () == 3)
                              m_glfcns.glColor3dv (col.data ());
                          }
                        m_glfcns.glVertex3d (m(0), m(1), m(2));
                      }

                    if (flag)
                      m_glfcns.glEnd ();
                  }
                else  // Normal edge contour drawn with tessellator
                  {
                    tess.begin_polygon (false);
                    tess.begin_contour ();

                    for (int j = count_f(i)-1; j >= 0; j--)
                      {
                        vertex_data::vertex_data_rep *vv
                          = vdata[i+j*fr].get_rep ();
                        tess.add_vertex (vv->coords.fortran_vec (), vv);
                      }

                    tess.end_contour ();
                    tess.end_polygon ();
                  }
              }

            set_linestyle ("-");  // Disable LineStipple
            set_linewidth (0.5f);

            if ((el_mode > 0) && do_lighting)
              m_glfcns.glDisable (GL_LIGHTING);
          }
        else
          {
            // FIXME: implement transparency
          }
      }

    if (! props.marker_is ("none")
        && ! (props.markeredgecolor_is ("none")
              && props.markerfacecolor_is ("none")))
      {
        bool do_edge = draw_all || ! props.markeredgecolor_is ("none");
        bool do_face = draw_all || ! props.markerfacecolor_is ("none");

        Matrix mecolor = (draw_all ? Matrix (1, 3, 0.0) :
                          props.get_markeredgecolor_rgb ());
        Matrix mfcolor = (draw_all ? Matrix (1, 3, 0.0) :
                          props.get_markerfacecolor_rgb ());

        bool has_markerfacecolor = draw_all || false;

        if ((mecolor.isempty () && ! props.markeredgecolor_is ("none"))
            || (mfcolor.isempty () && ! props.markerfacecolor_is ("none")))
          {
            Matrix mc = props.get_color_data ().matrix_value ();

            if (mc.rows () == 1)
              {
                // Single color specifications, we can simplify a little bit
                if (mfcolor.isempty () && ! props.markerfacecolor_is ("none"))
                  mfcolor = mc;

                if (mecolor.isempty () && ! props.markeredgecolor_is ("none"))
                  mecolor = mc;
              }
            else
              {
                if (c.isempty ())
                  c = props.get_color_data ().matrix_value ();
                has_markerfacecolor = ((c.numel () > 0)
                                       && (c.rows () == f.rows ()));
              }
          }

        init_marker (props.get_marker (), props.get_markersize (),
                     props.get_linewidth ());

        uint8_t clip_mask = (props.is_clipping () ? 0x7F : 0x40);
        uint8_t clip_ok = 0x40;

        for (int i = 0; i < nf; i++)
          for (int j = 0; j < count_f(i); j++)
            {
              int idx = int (f(i,j) - 1);

              if ((clip_code (v(idx,0), v(idx,1), (has_z ? v(idx,2) : 0))
                   & clip_mask) != clip_ok)
                continue;

              Matrix cc;
              if (c.numel () > 0)
                {
                  cc.resize (1, 3);
                  if (has_markerfacecolor)
                    cc(0) = c(i,0), cc(1) = c(i,1), cc(2) = c(i,2);
                  else
                    cc(0) = c(idx,0), cc(1) = c(idx,1), cc(2) = c(idx,2);
                }

              Matrix lc = (do_edge ? (mecolor.isempty () ? cc : mecolor)
                                   : Matrix ());
              Matrix fc = (do_face ? (mfcolor.isempty () ? cc : mfcolor)
                                   : Matrix ());

              draw_marker (v(idx,0), v(idx,1), (has_z ? v(idx,2) : 0), lc, fc);
            }

        end_marker ();
      }

#else

    octave_unused_parameter (props);

    // This shouldn't happen because construction of opengl_renderer
    // objects is supposed to be impossible if OpenGL is not available.

    panic_impossible ();

#endif
  }

  void
  opengl_renderer::draw_light (const light::properties& props)
  {
#if defined (HAVE_OPENGL)

    // enable light source
    m_glfcns.glEnable (m_current_light);

    // light position
    float pos[4] = { 0, 0, 0, 0 }; // X,Y,Z,infinite/local
    Matrix lpos = props.get_position ().matrix_value ();
    for (int i = 0; i < 3; i++)
      pos[i] = lpos(i);
    if (props.style_is ("local"))
      pos[3] = 1;
    m_glfcns.glLightfv (m_current_light, GL_POSITION, pos);

    // light color
    float col[4] = { 1, 1, 1, 1 }; // R,G,B,ALPHA (the latter has no meaning)
    Matrix lcolor = props.get_color ().matrix_value ();
    for (int i = 0; i < 3; i++)
      col[i] = lcolor(i);
    m_glfcns.glLightfv (m_current_light, GL_DIFFUSE,  col);
    m_glfcns.glLightfv (m_current_light, GL_SPECULAR, col);

#else

    octave_unused_parameter (props);

    // This shouldn't happen because construction of opengl_renderer
    // objects is supposed to be impossible if OpenGL is not available.

    panic_impossible ();

#endif
  }

  void
  opengl_renderer::draw_hggroup (const hggroup::properties& props)
  {
    draw (props.get_children ());
  }

  void
  opengl_renderer::draw_text (const text::properties& props)
  {
#if defined (HAVE_OPENGL)

    if (props.get_string ().isempty () || props.color_is ("none"))
      return;

    Matrix pos = xform.scale (props.get_data_position ());

    // Handle clipping manually when drawing text background
    if (! props.is_clipping ()
        || (clip_code (pos(0), pos(1), pos.numel () > 2 ? pos(2) : 0.0) == 0x40))
      {
        set_clipping (false);
        draw_text_background (props);
        set_clipping (props.is_clipping ());
      }

    set_font (props);

    const Matrix bbox = props.get_extent_matrix ();

    bool blend = m_glfcns.glIsEnabled (GL_BLEND);

    m_glfcns.glEnable (GL_BLEND);
    m_glfcns.glEnable (GL_ALPHA_TEST);
    m_glfcns.glRasterPos3d (pos(0), pos(1), pos.numel () > 2 ? pos(2) : 0.0);
    m_glfcns.glBitmap (0, 0, 0, 0, bbox(0), bbox(1), nullptr);
    m_glfcns.glDrawPixels (bbox(2), bbox(3), GL_RGBA, GL_UNSIGNED_BYTE,
                           props.get_pixels ().data ());
    m_glfcns.glDisable (GL_ALPHA_TEST);
    if (! blend)
      m_glfcns.glDisable (GL_BLEND);

#else

    octave_unused_parameter (props);

    // This shouldn't happen because construction of opengl_renderer
    // objects is supposed to be impossible if OpenGL is not available.

    panic_impossible ();

#endif
  }

  void
  opengl_renderer::draw_text_background (const text::properties& props,
                                         bool do_rotate)
  {
#if defined (HAVE_OPENGL)

    Matrix bgcol = props.get_backgroundcolor_rgb ();
    Matrix ecol = props.get_edgecolor_rgb ();

    if (bgcol.isempty () && ecol.isempty ())
      return;

    Matrix pos = props.get_data_position ();
    ColumnVector pixpos = get_transform ().transform (pos(0), pos(1),
                                                      pos(2), true);

    // Save current transform matrices and set orthogonal window coordinates
    m_glfcns.glMatrixMode (GL_PROJECTION);
    m_glfcns.glPushMatrix ();
    m_glfcns.glLoadIdentity ();

    Matrix vp = get_viewport_scaled ();
    m_glfcns.glOrtho (0, vp(2), vp(3), 0, xZ1, xZ2);
    m_glfcns.glMatrixMode (GL_MODELVIEW);
    m_glfcns.glPushMatrix ();
    m_glfcns.glLoadIdentity ();

    // Translate coordinates so that the text anchor is (0,0)
    m_glfcns.glTranslated (pixpos(0), pixpos(1), -pixpos(2));

    // FIXME: Only multiples of 90° are handled by the text renderer.
    //        Handle others here.
    double rotation = props.get_rotation ();

    if (do_rotate && rotation != 0.0 && rotation != 90.0
        && rotation != 180.0 && rotation != 270.0)
      m_glfcns.glRotated (-rotation, 0.0, 0.0, 1.0);

    double m = points_to_pixels (props.get_margin ());
    const Matrix bbox = props.get_extent_matrix ();
    double x0 = bbox (0) / m_devpixratio - m;
    double x1 = x0 + bbox(2) / m_devpixratio + 2 * m;
    double y0 = -(bbox (1) / m_devpixratio - m);
    double y1 = y0 - (bbox(3) / m_devpixratio + 2 * m);

    if (! bgcol.isempty ())
      {
        m_glfcns.glColor3f (bgcol(0), bgcol(1), bgcol(2));

        bool depth_test = m_glfcns.glIsEnabled (GL_DEPTH_TEST);
        if (depth_test)
          set_polygon_offset (true, 4.0);

        m_glfcns.glBegin (GL_QUADS);
        m_glfcns.glVertex2d (x0, y0);
        m_glfcns.glVertex2d (x1, y0);
        m_glfcns.glVertex2d (x1, y1);
        m_glfcns.glVertex2d (x0, y1);
        m_glfcns.glEnd ();

        if (depth_test)
          set_polygon_offset (false);
      }

    if (! ecol.isempty ())
      {
        m_glfcns.glColor3f (ecol(0), ecol(1), ecol(2));

        set_linestyle (props.get_linestyle (), false, props.get_linewidth ());
        set_linewidth (props.get_linewidth ());

        m_glfcns.glBegin (GL_LINE_STRIP);
        m_glfcns.glVertex2d (x0, y0);
        m_glfcns.glVertex2d (x1, y0);
        m_glfcns.glVertex2d (x1, y1);
        m_glfcns.glVertex2d (x0, y1);
        m_glfcns.glVertex2d (x0, y0);
        m_glfcns.glEnd ();

        set_linestyle ("-");
      }

    // Restore previous coordinate system
    m_glfcns.glPopMatrix();
    m_glfcns.glMatrixMode (GL_PROJECTION);
    m_glfcns.glPopMatrix();

#else

    octave_unused_parameter (props);
    octave_unused_parameter (do_rotate);

    // This shouldn't happen because construction of opengl_renderer
    // objects is supposed to be impossible if OpenGL is not available.

    panic_impossible ();

#endif
  }

  void
  opengl_renderer::draw_image (const image::properties& props)
  {
#if defined (HAVE_OPENGL)

    octave_value cdata = props.get_color_data ();
    dim_vector dv (cdata.dims ());
    int h = dv(0);
    int w = dv(1);
    double x0, x1, y0, y1;

    Matrix x = props.get_xdata ().matrix_value ();
    double dx = 1.0;
    if (w > 1)
      dx = (x(1) - x(0)) / (w - 1);

    x0 = x(0)-dx/2;
    x1 = x(1)+dx/2;

    Matrix y = props.get_ydata ().matrix_value ();
    double dy = 1.0;
    if (h > 1)
      dy = (y(1) - y(0)) / (h - 1);

    y0 = y(0)-dy/2;
    y1 = y(1)+dy/2;

    // Expect RGB data
    if (dv.ndims () == 3 && dv(2) == 3)
      {
        opengl_texture tex  = opengl_texture::create (m_glfcns, cdata);
        if (tex.is_valid ())
          {
            m_glfcns.glColor4d (1.0, 1.0, 1.0, 1.0);

            m_glfcns.glEnable (GL_TEXTURE_2D);

            m_glfcns.glBegin (GL_QUADS);

            tex.tex_coord (0.0, 0.0);
            m_glfcns.glVertex3d (x0, y0, 0.0);

            tex.tex_coord (1.0, 0.0);
            m_glfcns.glVertex3d (x1, y0, 0.0);

            tex.tex_coord (1.0, 1.0);
            m_glfcns.glVertex3d (x1, y1, 0.0);

            tex.tex_coord (0.0, 1.0);
            m_glfcns.glVertex3d (x0, y1, 0.0);

            m_glfcns.glEnd ();
            m_glfcns.glDisable (GL_TEXTURE_2D);
          }
      }
    else
      warning ("opengl_renderer: invalid image size (expected MxNx3 or MxN)");

#else

    octave_unused_parameter (props);

    // This shouldn't happen because construction of opengl_renderer
    // objects is supposed to be impossible if OpenGL is not available.

    panic_impossible ();

#endif
  }

  void opengl_renderer::draw (const Matrix& hlist, bool toplevel)
  {
    int len = hlist.numel ();

    gh_manager& gh_mgr = __get_gh_manager__ ("opengl_renderer::draw");

    for (int i = len-1; i >= 0; i--)
      {
        graphics_object obj = gh_mgr.get_object (hlist(i));

        if (obj)
          draw (obj, toplevel);
      }
  }

  void
  opengl_renderer::set_viewport (int w, int h)
  {
#if defined (HAVE_OPENGL)

    m_glfcns.glViewport (0, 0, w, h);

#else

    octave_unused_parameter (w);
    octave_unused_parameter (h);

    // This shouldn't happen because construction of opengl_renderer
    // objects is supposed to be impossible if OpenGL is not available.

    panic_impossible ();

#endif
  }

  Matrix
  opengl_renderer::get_viewport_scaled (void) const
  {
    Matrix retval (1, 4, 0.0);

#if defined (HAVE_OPENGL)
#if defined (HAVE_FRAMEWORK_OPENGL)
    GLint vp[4];
#else
    int vp[4];
#endif

    m_glfcns.glGetIntegerv (GL_VIEWPORT, vp);

    for (int i = 0; i < 4; i++)
      retval(i) = static_cast<double> (vp[i]) / m_devpixratio;

#else

    // This shouldn't happen because construction of opengl_renderer
    // objects is supposed to be impossible if OpenGL is not available.

    panic_impossible ();

#endif

    return retval;
  }

  void
  opengl_renderer::set_color (const Matrix& c)
  {
#if defined (HAVE_OPENGL)

    m_glfcns.glColor3dv (c.data ());

    if (! c.isempty ())
      txt_renderer.set_color (c);

#else

    octave_unused_parameter (c);

    // This shouldn't happen because construction of opengl_renderer
    // objects is supposed to be impossible if OpenGL is not available.

    panic_impossible ();

#endif
  }

  void
  opengl_renderer::set_font (const base_properties& props)
  {
    bool do_anti_alias = props.get ("fontsmoothing").string_value () == "on";
    txt_renderer.set_anti_aliasing (do_anti_alias);
    txt_renderer.set_font (props.get ("fontname").string_value (),
                           props.get ("fontweight").string_value (),
                           props.get ("fontangle").string_value (),
                           props.get ("__fontsize_points__").double_value ()
                           * m_devpixratio);
  }

  void
  opengl_renderer::set_polygon_offset (bool on, float offset)
  {
#if defined (HAVE_OPENGL)

    if (on)
      {
        m_glfcns.glEnable (GL_POLYGON_OFFSET_FILL);
        m_glfcns.glEnable (GL_POLYGON_OFFSET_LINE);
        m_glfcns.glPolygonOffset (offset, offset);
      }
    else
      {
        m_glfcns.glDisable (GL_POLYGON_OFFSET_FILL);
        m_glfcns.glDisable (GL_POLYGON_OFFSET_LINE);
      }

#else

    octave_unused_parameter (on);
    octave_unused_parameter (offset);

    // This shouldn't happen because construction of opengl_renderer
    // objects is supposed to be impossible if OpenGL is not available.

    panic_impossible ();

#endif
  }

  void
  opengl_renderer::set_linewidth (float w)
  {
#if defined (HAVE_OPENGL)
    // Measure LineWidth in points.  See bug #53056.
    m_glfcns.glLineWidth (points_to_pixels (w) * m_devpixratio);

#else

    octave_unused_parameter (w);

    // This shouldn't happen because construction of opengl_renderer
    // objects is supposed to be impossible if OpenGL is not available.

    panic_impossible ();

#endif
  }

  void
  opengl_renderer::set_linestyle (const std::string& s, bool use_stipple,
                                  double linewidth)
  {
#if defined (HAVE_OPENGL)
    // Measure LineWidth in points.  See bug #53056.
    int factor = math::round (points_to_pixels (linewidth) * m_devpixratio);
    if (factor < 1)
      factor = 1;

    uint16_t pattern = 0xFFFF;

    bool solid = false;

    if (s == "-")
      solid = true;
    else if (s == ":")
      {
        if (factor > 1)
          pattern = 0x5555;
        else
          pattern = 0x1111;
      }
    else if (s == "--")
      {
        if (factor > 1)
          pattern = 0x0F0F;
        else
          pattern = 0x01FF;
      }
    else if (s == "-.")
      {
        if (factor > 1)
          pattern = 0x6F6F;
        else
          pattern = 0x18FF;
      }
    else
      pattern = 0x0000;

    m_glfcns.glLineStipple (factor, pattern);

    if (solid && ! use_stipple)
      m_glfcns.glDisable (GL_LINE_STIPPLE);
    else
      m_glfcns.glEnable (GL_LINE_STIPPLE);

#else

    octave_unused_parameter (s);
    octave_unused_parameter (use_stipple);
    octave_unused_parameter (linewidth);

    // This shouldn't happen because construction of opengl_renderer
    // objects is supposed to be impossible if OpenGL is not available.

    panic_impossible ();

#endif
  }

  void
  opengl_renderer::set_clipbox (double x1, double x2, double y1, double y2,
                                double z1, double z2)
  {
#if defined (HAVE_OPENGL)

    double dx = (x2-x1);
    double dy = (y2-y1);
    double dz = (z2-z1);

    x1 -= 0.001*dx; x2 += 0.001*dx;
    y1 -= 0.001*dy; y2 += 0.001*dy;
    z1 -= 0.001*dz; z2 += 0.001*dz;

    ColumnVector p (4, 0.0);

    p(0) = -1; p(3) = x2;
    m_glfcns.glClipPlane (GL_CLIP_PLANE0, p.data ());
    p(0) = 1; p(3) = -x1;
    m_glfcns.glClipPlane (GL_CLIP_PLANE1, p.data ());
    p(0) = 0; p(1) = -1; p(3) = y2;
    m_glfcns.glClipPlane (GL_CLIP_PLANE2, p.data ());
    p(1) = 1; p(3) = -y1;
    m_glfcns.glClipPlane (GL_CLIP_PLANE3, p.data ());
    p(1) = 0; p(2) = -1; p(3) = z2;
    m_glfcns.glClipPlane (GL_CLIP_PLANE4, p.data ());
    p(2) = 1; p(3) = -z1;
    m_glfcns.glClipPlane (GL_CLIP_PLANE5, p.data ());

    xmin = x1; xmax = x2;
    ymin = y1; ymax = y2;
    zmin = z1; zmax = z2;

#else

    octave_unused_parameter (x1);
    octave_unused_parameter (x2);
    octave_unused_parameter (y1);
    octave_unused_parameter (y2);
    octave_unused_parameter (z1);
    octave_unused_parameter (z2);

    // This shouldn't happen because construction of opengl_renderer
    // objects is supposed to be impossible if OpenGL is not available.

    panic_impossible ();

#endif
  }

  void
  opengl_renderer::set_clipping (bool enable)
  {
#if defined (HAVE_OPENGL)

    bool has_clipping = (m_glfcns.glIsEnabled (GL_CLIP_PLANE0) == GL_TRUE);

    if (enable != has_clipping)
      {
        if (enable)
          for (int i = 0; i < 6; i++)
            m_glfcns.glEnable (GL_CLIP_PLANE0+i);
        else
          for (int i = 0; i < 6; i++)
            m_glfcns.glDisable (GL_CLIP_PLANE0+i);
      }

#else

    octave_unused_parameter (enable);

    // This shouldn't happen because construction of opengl_renderer
    // objects is supposed to be impossible if OpenGL is not available.

    panic_impossible ();

#endif
  }

  void
  opengl_renderer::init_marker (const std::string& m, double size, float width)
  {
#if defined (HAVE_OPENGL)
    m_glfcns.glMatrixMode (GL_PROJECTION);
    m_glfcns.glPushMatrix ();
    m_glfcns.glLoadIdentity ();

    Matrix vp = get_viewport_scaled ();
    m_glfcns.glOrtho (0, vp(2), vp(3), 0, xZ1, xZ2);
    m_glfcns.glMatrixMode (GL_MODELVIEW);
    m_glfcns.glPushMatrix ();

    set_clipping (false);
    set_linewidth (width);

    marker_id = make_marker_list (m, size, false);
    filled_marker_id = make_marker_list (m, size, true);

#else

    octave_unused_parameter (m);
    octave_unused_parameter (size);
    octave_unused_parameter (width);

    // This shouldn't happen because construction of opengl_renderer
    // objects is supposed to be impossible if OpenGL is not available.

    panic_impossible ();

#endif
  }

  void
  opengl_renderer::end_marker (void)
  {
#if defined (HAVE_OPENGL)

    m_glfcns.glDeleteLists (marker_id, 1);
    m_glfcns.glDeleteLists (filled_marker_id, 1);

    m_glfcns.glMatrixMode (GL_MODELVIEW);
    m_glfcns.glPopMatrix ();
    m_glfcns.glMatrixMode (GL_PROJECTION);
    m_glfcns.glPopMatrix ();
    set_linewidth (0.5f);

#else

    // This shouldn't happen because construction of opengl_renderer
    // objects is supposed to be impossible if OpenGL is not available.

    panic_impossible ();

#endif
  }

  void
  opengl_renderer::draw_marker (double x, double y, double z,
                                const Matrix& lc, const Matrix& fc)
  {
#if defined (HAVE_OPENGL)

    ColumnVector tmp = xform.transform (x, y, z, false);

    m_glfcns.glLoadIdentity ();
    m_glfcns.glTranslated (tmp(0), tmp(1), -tmp(2));

    if (filled_marker_id > 0 && fc.numel () > 0)
      {
        m_glfcns.glColor3dv (fc.data ());
        set_polygon_offset (true, -1.0);
        m_glfcns.glCallList (filled_marker_id);
        if (lc.numel () > 0)
          {
            m_glfcns.glColor3dv (lc.data ());
            m_glfcns.glPolygonMode (GL_FRONT_AND_BACK, GL_LINE);
            m_glfcns.glEdgeFlag (GL_TRUE);
            set_polygon_offset (true, -2.0);
            m_glfcns.glCallList (filled_marker_id);
            m_glfcns.glPolygonMode (GL_FRONT_AND_BACK, GL_FILL);
          }
        set_polygon_offset (false);
      }
    else if (marker_id > 0 && lc.numel () > 0)
      {
        m_glfcns.glColor3dv (lc.data ());
        m_glfcns.glCallList (marker_id);
      }

#else

    octave_unused_parameter (x);
    octave_unused_parameter (y);
    octave_unused_parameter (z);
    octave_unused_parameter (lc);
    octave_unused_parameter (fc);

    // This shouldn't happen because construction of opengl_renderer
    // objects is supposed to be impossible if OpenGL is not available.

    panic_impossible ();

#endif
  }

  void
  opengl_renderer::init_maxlights (void)
  {
#if defined (HAVE_OPENGL)

    // Check actual maximum number of lights possible
    if (m_max_lights == 0)
      {
        GLint max_lights;
        m_glfcns.glGetIntegerv (GL_MAX_LIGHTS, &max_lights);
        m_max_lights = max_lights;
      }

#else

    // This shouldn't happen because construction of opengl_renderer
    // objects is supposed to be impossible if OpenGL is not available.

    panic_impossible ();

#endif
  }

  std::string
  opengl_renderer::get_string (unsigned int id) const
  {
#if defined (HAVE_OPENGL)

    // This is kind of ugly, but glGetString returns a pointer to GLubyte
    // and there is no std::string constructor that matches.  Is there a
    // better way?

    std::ostringstream buf;

    buf << m_glfcns.glGetString (static_cast<GLenum> (id));

    return std::string (buf.str ());

#else

    octave_unused_parameter (id);

    // This shouldn't happen because construction of opengl_renderer
    // objects is supposed to be impossible if OpenGL is not available.

    panic_impossible ();
    return std::string ();

#endif
  }

  void
  opengl_renderer::set_normal (int bfl_mode, const NDArray& n, int j, int i)
  {
#if defined (HAVE_OPENGL)

    double x = n(j,i,0);
    double y = n(j,i,1);
    double z = n(j,i,2);

    double d = sqrt (x*x + y*y + z*z);

    double dir = 1.0;

    if (bfl_mode > 0)
      dir = ((x * view_vector(0) + y * view_vector(1) + z * view_vector(2) < 0)
             ? ((bfl_mode > 1) ? 0.0 : -1.0) : 1.0);

    m_glfcns.glNormal3d (dir*x/d, dir*y/d, dir*z/d);

#else

    octave_unused_parameter (bfl_mode);
    octave_unused_parameter (n);
    octave_unused_parameter (j);
    octave_unused_parameter (i);

    // This shouldn't happen because construction of opengl_renderer
    // objects is supposed to be impossible if OpenGL is not available.

    panic_impossible ();

#endif
  }

  double
  opengl_renderer::points_to_pixels (const double val) const
  {
    gh_manager& gh_mgr = __get_gh_manager__ ("opengl_renderer::points_to_pixels");

    // FIXME: Does making this static cause problems if figure is moved to a
    //        2nd monitor with a different value for "screenpixelsperinch"?
    static const double pix_per_pts =
      gh_mgr.get_object (0).get ("screenpixelsperinch").double_value () / 72.0;

    double retval = val;

    if (! m_printing)
      retval *= pix_per_pts;

    return retval;
  }

  unsigned int
  opengl_renderer::make_marker_list (const std::string& marker, double size,
                                     bool filled) const
  {
#if defined (HAVE_OPENGL)

    char c = marker[0];

    if (filled && (c == '+' || c == 'x' || c == '*' || c == '.'))
      return 0;

    unsigned int ID = m_glfcns.glGenLists (1);

    // FIXME: See bug #53056 (measure LineWidth in points).
    double sz = points_to_pixels (size);

    // constants for the * marker
    const double sqrt2d4 = 0.35355339059327;
    double tt = sz*sqrt2d4;

    m_glfcns.glNewList (ID, GL_COMPILE);

    switch (marker[0])
      {
      case '+':
        m_glfcns.glBegin (GL_LINES);
        m_glfcns.glVertex2d (-sz/2, 0);
        m_glfcns.glVertex2d (sz/2, 0);
        m_glfcns.glVertex2d (0, -sz/2);
        m_glfcns.glVertex2d (0, sz/2);
        m_glfcns.glEnd ();
        break;
      case 'x':
        m_glfcns.glBegin (GL_LINES);
        m_glfcns.glVertex2d (-sz/2, -sz/2);
        m_glfcns.glVertex2d (sz/2, sz/2);
        m_glfcns.glVertex2d (-sz/2, sz/2);
        m_glfcns.glVertex2d (sz/2, -sz/2);
        m_glfcns.glEnd ();
        break;
      case '*':
        m_glfcns.glBegin (GL_LINES);
        m_glfcns.glVertex2d (-sz/2, 0);
        m_glfcns.glVertex2d (sz/2, 0);
        m_glfcns.glVertex2d (0, -sz/2);
        m_glfcns.glVertex2d (0, sz/2);
        m_glfcns.glVertex2d (-tt, -tt);
        m_glfcns.glVertex2d (+tt, +tt);
        m_glfcns.glVertex2d (-tt, +tt);
        m_glfcns.glVertex2d (+tt, -tt);
        m_glfcns.glEnd ();
        break;
      case '.':
        {
          // The dot marker is special and is drawn at 1/3rd the specified size

          // Ensure that something is drawn even at very small markersizes
          if (sz > 0 && sz < 3)
            sz = 3;

          int div = static_cast<int> (M_PI * sz / 12);
          if (! (div % 2))
            div += 1;               // ensure odd number for left/right symmetry
          div = std::max (div, 3);  // ensure at least a few vertices are drawn
          double ang_step = M_PI / div;

          m_glfcns.glBegin (GL_POLYGON);
          for (double ang = 0; ang < 2*M_PI; ang += ang_step)
            m_glfcns.glVertex2d (sz/6*cos (ang), sz/6*sin (ang));
          m_glfcns.glEnd ();
        }
        break;
      case 's':
        m_glfcns.glBegin (filled ? GL_POLYGON : GL_LINE_LOOP);
        m_glfcns.glVertex2d (-sz/2, -sz/2);
        m_glfcns.glVertex2d (-sz/2, sz/2);
        m_glfcns.glVertex2d (sz/2, sz/2);
        m_glfcns.glVertex2d (sz/2, -sz/2);
        m_glfcns.glEnd ();
        break;
      case 'o':
        {
          int div = static_cast<int> (M_PI * sz / 4);
          if (! (div % 2))
            div += 1;               // ensure odd number for left/right symmetry
          div = std::max (div, 5);  // ensure at least a few vertices are drawn
          double ang_step = M_PI / div;

          m_glfcns.glBegin (filled ? GL_POLYGON : GL_LINE_LOOP);
          for (double ang = 0; ang < 2*M_PI; ang += ang_step)
            m_glfcns.glVertex2d (sz/2*cos (ang), sz/2*sin (ang));
          m_glfcns.glEnd ();
        }
        break;
      case 'd':
        m_glfcns.glBegin (filled ? GL_POLYGON : GL_LINE_LOOP);
        m_glfcns.glVertex2d (0, -sz/2);
        m_glfcns.glVertex2d (sz/2, 0);
        m_glfcns.glVertex2d (0, sz/2);
        m_glfcns.glVertex2d (-sz/2, 0);
        m_glfcns.glEnd ();
        break;
      case 'v':
        m_glfcns.glBegin (filled ? GL_POLYGON : GL_LINE_LOOP);
        m_glfcns.glVertex2d (0, sz/2);
        m_glfcns.glVertex2d (sz/2, -sz/2);
        m_glfcns.glVertex2d (-sz/2, -sz/2);
        m_glfcns.glEnd ();
        break;
      case '^':
        m_glfcns.glBegin (filled ? GL_POLYGON : GL_LINE_LOOP);
        m_glfcns.glVertex2d (0, -sz/2);
        m_glfcns.glVertex2d (-sz/2, sz/2);
        m_glfcns.glVertex2d (sz/2, sz/2);
        m_glfcns.glEnd ();
        break;
      case '>':
        m_glfcns.glBegin (filled ? GL_POLYGON : GL_LINE_LOOP);
        m_glfcns.glVertex2d (sz/2, 0);
        m_glfcns.glVertex2d (-sz/2, sz/2);
        m_glfcns.glVertex2d (-sz/2, -sz/2);
        m_glfcns.glEnd ();
        break;
      case '<':
        m_glfcns.glBegin (filled ? GL_POLYGON : GL_LINE_LOOP);
        m_glfcns.glVertex2d (-sz/2, 0);
        m_glfcns.glVertex2d (sz/2, -sz/2);
        m_glfcns.glVertex2d (sz/2, sz/2);
        m_glfcns.glEnd ();
        break;
      case 'p':
        {
          double ang, r, dr;
          dr = 1.0 - sin (M_PI/10)/sin (3*M_PI/10)*1.02;

          m_glfcns.glBegin (filled ? GL_POLYGON : GL_LINE_LOOP);
          for (int i = 0; i < 2*5; i++)
            {
              ang = (-0.5 + double (i+1) / 5) * M_PI;
              r = 1.0 - (dr * fmod (double (i+1), 2.0));
              m_glfcns.glVertex2d (sz/2*r*cos (ang), sz/2*r*sin (ang));
            }
          m_glfcns.glEnd ();
        }
        break;
      case 'h':
        {
          double ang, r, dr;
          dr = 1.0 - 0.5/sin (M_PI/3)*1.02;

          m_glfcns.glBegin (filled ? GL_POLYGON : GL_LINE_LOOP);
          for (int i = 0; i < 2*6; i++)
            {
              ang = (0.5 + double (i+1) / 6.0) * M_PI;
              r = 1.0 - (dr * fmod (double (i+1), 2.0));
              m_glfcns.glVertex2d (sz/2*r*cos (ang), sz/2*r*sin (ang));
            }
          m_glfcns.glEnd ();
        }
        break;
      default:
        warning ("opengl_renderer: unsupported marker '%s'", marker.c_str ());
        break;
      }

    m_glfcns.glEndList ();

    return ID;

#else

    octave_unused_parameter (marker);
    octave_unused_parameter (size);
    octave_unused_parameter (filled);

    // This shouldn't happen because construction of opengl_renderer
    // objects is supposed to be impossible if OpenGL is not available.

    panic_impossible ();

#endif
  }

  void
  opengl_renderer::text_to_pixels (const std::string& txt,
                                   uint8NDArray& pixels,
                                   Matrix& bbox,
                                   int halign, int valign, double rotation)
  {
    txt_renderer.text_to_pixels (txt, pixels, bbox, halign, valign,
                                 rotation, interpreter);
  }

  void
  opengl_renderer::text_to_strlist (const std::string& txt,
                                    std::list<text_renderer::string>& lst,
                                    Matrix& bbox,
                                    int halign, int valign, double rotation)
  {
    txt_renderer.text_to_strlist (txt, lst, bbox, halign, valign,
                                  rotation, interpreter);
  }

  Matrix
  opengl_renderer::render_text (const std::string& txt,
                                double x, double y, double z,
                                int halign, int valign, double rotation)
  {
#if defined (HAVE_OPENGL)

    Matrix bbox (1, 4, 0.0);

    if (txt.empty ())
      return bbox;

    if (txt_renderer.ok ())
      {
        uint8NDArray pixels;
        text_to_pixels (txt, pixels, bbox, halign, valign, rotation);

        bool blend = m_glfcns.glIsEnabled (GL_BLEND);

        m_glfcns.glEnable (GL_BLEND);
        m_glfcns.glEnable (GL_ALPHA_TEST);
        m_glfcns.glRasterPos3d (x, y, z);
        m_glfcns.glBitmap(0, 0, 0, 0, bbox(0), bbox(1), nullptr);
        m_glfcns.glDrawPixels (bbox(2), bbox(3),
                               GL_RGBA, GL_UNSIGNED_BYTE, pixels.data ());
        m_glfcns.glDisable (GL_ALPHA_TEST);

        if (! blend)
          m_glfcns.glDisable (GL_BLEND);
      }

    return bbox;

#else

    octave_unused_parameter (txt);
    octave_unused_parameter (x);
    octave_unused_parameter (y);
    octave_unused_parameter (z);
    octave_unused_parameter (halign);
    octave_unused_parameter (valign);
    octave_unused_parameter (rotation);

    // This shouldn't happen because construction of opengl_renderer
    // objects is supposed to be impossible if OpenGL is not available.

    panic_impossible ();

#endif
  }
}